How to Play the Gsus Guitar Chord (Gsus2 and Gsus4)

"Gsus" almost always means one of two chords: Gsus4 (fret the 6th string 3rd fret, the 5th string 3rd fret, the 2nd string 1st fret, leave the 4th and 3rd strings open, and fret the 1st string 3rd fret) or Gsus2 (the same low E and high E notes, but leave the 5th string open and fret only the 2nd string at the 3rd fret). Both swap out the note that makes G major sound "major," which is why a Gsus chord sounds unfinished, restless, like it wants to go somewhere. Here is exactly where each finger goes, why the sound comes out wrong, and how to move into and out of it without stopping the song.

What "sus" actually means, in one paragraph

A G major chord is built from three notes: G (the root), B (the 3rd), and D (the 5th). That B is the note doing all the work, it is what makes the chord sound happy and resolved rather than tense. "Sus" is short for suspended, and a suspended chord replaces that 3rd with a different note, either the note one step above the root (the 2nd, giving Gsus2: G, A, D) or the note one step below the 5th (the 4th, giving Gsus4: G, C, D). Neither version contains a 3rd of any kind, major or minor, which is exactly why a sus chord sounds neither happy nor sad. It sounds like a held breath, waiting for the 3rd to come back.

Where the word "suspended" actually comes from

The term is not guitar slang, it is borrowed directly from classical harmony, where it names a specific technique called a 4-3 suspension. In that technique, a note from the previous chord is held, or "suspended," over into the new chord for a beat before stepping down to the note the ear expects, creating a moment of dissonance that is prepared, held, and then resolved downward by a single step. A 4-3 suspension specifically means a 4th above the bass note hangs on before falling to the 3rd, which is exactly what Gsus4 does harmonically: the 4th (C) is held where the 3rd (B) would normally sit, and it wants to fall one step down to B the way a classical suspension resolves. Guitarists do not usually think about it in these terms, the shape is just called "Gsus4" and left to ring or resolve as the song requires, but the pull you hear when a Gsus4 moves back to G is the same effect composers were using centuries before the electric guitar existed. It is also why a sus chord that never resolves can start to sound like a mistake rather than a choice, the ear has been trained for hundreds of years to expect that fall.

String names and numbers, so the tables below make sense

Every fret and finger listed in this post refers to the six strings by both number and name, so it helps to have this settled first.

Strings are numbered from thinnest to thickest, so the 1st string is the high E string nearest the floor when the guitar is in playing position, and the 6th string is the thick low E string nearest the ceiling. Standard tuning, low to high, is E-A-D-G-B-E. Fret numbers count from the nut, the strip at the very top of the neck where the strings first make contact, so the "3rd fret" is the third space down the neck, not the third metal wire. Finger numbers follow the usual convention: 1 is the index finger, 2 is the middle finger, 3 is the ring finger, 4 is the pinky, and T marks the thumb where it comes up.

How to play Gsus4, the open-position shape

This is the version most players mean when they just say "Gsus," and the one worth learning first. It keeps the same root notes as an open G chord on the low E and high E strings, so your hand already half-knows this shape if you can already play G.

Strum all six strings. The two fretted notes on the outside (low E and high E, both at the 3rd fret) are the root, G, played an octave apart. The A string at the 3rd fret is the 4th, C. The B string at the 1st fret is also the 4th, C, an octave above the note on the A string. The D and G strings stay open, each contributing the 5th and root respectively, so nothing needs to be fretted there at all. Play the four fretted notes and let the two open strings ring underneath them, and every string should be doing exactly one job: root, 4th, 5th, root, 4th, root, from low to high.

How to play Gsus2, the open-position shape

Gsus2 uses almost the identical shape as Gsus4, with one important difference: instead of fretting the A string, you leave it open.

Here the open A string supplies the 2nd (A is the note A, which sits a whole step above G, the note that gives Gsus2 its name). The B string moves from the 1st fret used in Gsus4 up to the 3rd fret, which changes that string's note from C (the 4th) to D (the 5th), doubling the D that is already ringing open on the D string. Notice the pattern: Gsus4 and Gsus2 only ever disagree on the A string and the B string. The low E, D, G, and high E strings are identical in both chords, which is the whole reason they are easy to confuse and, once you see it, easy to switch between.

The one shortcut that makes both shapes click

Once you notice that Gsus2 and Gsus4 share four of six strings, learning them together is faster than learning them apart. Fret the shared shape first: middle finger on the low E string 3rd fret, pinky on the high E string 3rd fret, and leave the D and G strings alone entirely, they are always open in both chords. That shape alone, strummed on its own, already sounds like a thin, ambiguous "sus" chord even with the A and B strings muted or ignored. From there:

• Add the ring finger to the A string, 3rd fret, and you have Gsus4's A-string note.
• Add the index finger to the B string, 1st fret, and Gsus4 is complete.
• Or leave the A string open and move a finger to the B string's 3rd fret instead, and you have Gsus2.

Practicing it in that order, shared shape first, then the one or two notes that make it Gsus4 or Gsus2, is a faster way to internalize both chords than memorizing two separate six-string diagrams.

Reading Gsus4 in tab notation

Chord charts show Gsus4 as a diagram or a table like the ones above, but tab notation writes the same shape as a column of fret numbers, one per string, read low E to high E. Gsus4's open-position shape looks like this:

e|-3-
B|-1-
G|-0-
D|-0-
A|-3-
E|-3-

Read top to bottom that is high E, B, G, D, A, low E, the order tab is conventionally written in, which is the reverse of the string-number order used in the tables elsewhere in this post. The dash on the G and D strings shows an open string, not a muted one, both are meant to ring. Gsus2's tab looks almost identical, with only the A and B string lines changed:

e|-3-
B|-3-
G|-0-
D|-0-
A|-0-
E|-3-

Recognizing this pattern is useful beyond this one chord, most tab archives write chords this way rather than as a labeled diagram, so being able to translate a column of six numbers into a fingering on sight saves time on every chord chart afterward, not just this one.

A strumming pattern that shows off the suspension

Because a sus chord's whole effect depends on the ear noticing the tension and then hearing it resolve, how you strum it matters as much as which notes are in it. A simple, effective pattern for practicing the G to Gsus4 movement is down, down-up, up, down-up, played once on G and once on Gsus4 before the next chord change, roughly one full pattern per two beats at a moderate tempo. Slowing the strum right down to a single sustained downstroke on the Gsus4 before resolving to G is another common approach, especially in a slower ballad-style song, since it gives the suspended note time to actually register with the listener before it falls away. Strumming Gsus4 exactly like a plain G chord, at the same speed and with the same accents, is the most common reason the suspension goes unnoticed even when every finger is in the right place, the ear needs a beat of space to register that something has changed.

Fingerpicking Gsus4 and Gsus2

Both shapes fingerpick cleanly because four of their six strings, including both open strings, do not need the fretting hand to do anything different from a plain G or C pattern. A common arpeggio order for Gsus4 is thumb on the low E string, then index on the D string, middle on the G string, ring on the B string, and back down through the D string before repeating, which lets the open D and G strings ring into each other while the C notes on the A and B strings color the pattern without needing to be picked in every repetition. Because the D and G strings are open in both Gsus4 and Gsus2, a fingerpicking pattern built around this chord can often move between the two just by changing which string the ring finger picks, the A string for Gsus2's open A, the same B string fret for Gsus4's C, without altering the thumb or index pattern underneath at all.

Using a capo with Gsus4

A capo does not remove any note from a chord shape, it only changes which actual pitch that shape produces, so the open Gsus4 fingering played behind a capo is still structurally a sus4 chord, just transposed to a different letter name.

This matters most when a chord chart calls for a sus4 chord on a different root than G but the fingering given is awkward, since capoing up and playing the familiar Gsus4 shape by hand is often easier than learning a brand new fingering for, say, Csus4 in open position. The tradeoff is that everything else you play also transposes with the capo, so this only works cleanly when the whole song is being capoed, not for switching a single chord mid-progression.

Why it buzzes or sounds muted

A sus chord has fewer notes doing more work than a full major or minor chord, so a single bad note stands out more than it would in a fuller-sounding G or C. These are the specific causes, one at a time.

The B-string finger is too far from the fret

On Gsus4, the index finger on the 2nd string sits at the 1st fret, the fret closest to the nut where the frets are widest apart and the string tension is highest. Press too far from the fret wire, back toward the nut, and the note buzzes or does not ring at all. Move that fingertip right up against the 1st fret wire itself, not into the middle of the fret space, and the buzz usually disappears immediately.

The middle finger on the low E string is flattening onto the A string

The middle finger frets the low E string at the 3rd fret in both shapes. If that finger's tip is not arched enough, the pad of the finger can lean over and lightly touch the A string, muting or muffling the note the ring finger (or an open string, in Gsus2) is trying to produce next to it. Arch the middle finger so only its very tip contacts the low E string, leaving the neighboring string completely clear.

The ring finger is too flat on Gsus4's A string note

The ring finger's job on Gsus4, fretting the A string at the 3rd fret, sits right beside the open D string. A ring finger that lies flat instead of coming down on its tip will deaden that open D string the moment you fret the A string, and the chord loses its 5th. Curl the ring finger so its knuckle stays clear of the D string entirely.

The pinky is the weakest finger and it shows

The pinky frets the high E string at the 3rd fret in every version of this chord, and it is the finger most players have the least independent control over. A pinky that presses at an angle, rather than straight down onto the string, produces a weak or buzzy top note that gets lost in the strum. Practice fretting that note by itself, picking only the high E string, until it rings as cleanly on its own as the other five strings do together.

An open string is being caught by an adjacent finger

Because Gsus4 and Gsus2 both rely on two genuinely open strings (D and G) ringing next to fretted ones, it is easy for a finger meant for the A or B string to drift and rest against the open string beside it without you noticing, since the chord still sounds "mostly right." Strum slowly, one string at a time, immediately after fretting the chord, and listen for any string that comes out muted, dead, or buzzing rather than ringing clearly. That single check catches most Gsus problems before they become a habit.

The fingers are tensed and tiring partway through a song

A chord that rings clean for the first few bars and then starts to buzz later in a song is rarely a fingering problem, it is a grip problem. Pressing harder than a string actually needs tires the hand and causes the fretting fingers to lose precise position as the muscles fatigue, which shows up as new buzzing on notes that were clean minutes earlier. The fix is not more pressure, it is less: press only hard enough for the string to ring clearly and no harder, so the hand can sustain that same light pressure for an entire song rather than the first minute of it.

The guitar's own setup is working against you

If every chord on the guitar buzzes a little, not just Gsus4 and Gsus2, the cause is likely the instrument rather than the fingering. Strings sitting unusually low over the frets (low "action") make any chord easier to fret but more prone to buzzing, especially on notes near the nut like the B string's 1st fret in Gsus4. This is worth ruling out before assuming a fingering problem: try the same shape a few frets higher up the neck, where buzzing from low action is less pronounced, and if the chord suddenly rings cleaner up there, the guitar's setup, not your hand, is the thing to address.

Common progressions built around Gsus4

Gsus4 rarely appears on its own in a chord chart, it almost always sits directly beside the plain G chord it decorates, or beside C and D, the two chords it shares the most notes with. A few patterns come up often enough to be worth practicing as their own unit rather than meeting them cold inside a full song.

Playing through each row slowly, listening for what specifically the Gsus4 adds before the next chord arrives, is a faster way to internalize why the chord gets used than memorizing the shape alone.

Easier alternatives if the stretch feels awkward

Neither Gsus4 nor Gsus2 requires a stretch, both fit inside three frets, but a few adjustments make them friendlier for smaller hands or players still building independent finger control.

Drop the A string from Gsus4

If keeping the ring finger clean on the A string while the D string rings open beside it is the sticking point, simplify Gsus4 by muting or simply not strumming the A string entirely.

This drops the doubled root on the low E string too, so what is left is a lighter, higher-register version built from just the D string, the open G, the C on the B string, and the G on the high E. It still spells out the same three notes, D, G, C, just without the low end, and it is genuinely easier to strum cleanly since there are only two fingers to manage.

A two-finger version of Gsus2

Gsus2 simplifies even further, since two of its four active strings are already open.

Using index, middle, and ring instead of middle, ring, and pinky is a small change, but it moves the weakest finger, the pinky, out of the chord entirely, which is worth trying if the pinky is the finger giving you the most trouble on the standard fingering.

The moveable barre version, further up the neck

Both Gsus4 and Gsus2 also exist as moveable shapes built on the same barre pattern used for E-shape major chords, which means the same fingering can be slid up and down the neck to play a sus4 or sus2 chord rooted on any string. For G specifically, rooted on the 6th string, the barre sits at the 3rd fret.

The index finger barres straight across all six strings at the 3rd fret, exactly as it would for a barred G major or G minor. A second finger, usually the ring finger, then lays flat across just the A, D, and G strings two frets higher, at the 5th fret, forming a small three-string mini-barre. That mini-barre is what changes the chord from major to sus4, it lifts the 3rd out and replaces it with the 4th on the middle three strings while the barred low E, B, and high E strings keep supplying the root and 5th unchanged. This shape takes real finger independence to fret cleanly and is worth coming back to once the open-position version feels solid, not before. It is not a shortcut, it is the same chord rebuilt on a movable frame, useful mainly once you want a Gsus4 that sits higher in the mix than the open version, or a capoed-sounding voicing without a capo.

Gsus4, Gadd4, and G7sus4: chords that get confused with it

A few chord names look close enough to Gsus4 to cause mix-ups. They are not interchangeable.

Gadd4 sounds noticeably busier and more dissonant than Gsus4 because it keeps both the major 3rd and the 4th ringing at once, a half step apart, which is a much harsher clash than either chord alone. G7sus4 is common in funk and R&B rhythm playing, it keeps the suspended, unresolved character of Gsus4 but adds the same flat 7th that turns G into G7, which is why it is written and heard far more often in that style than in folk or pop strumming.

Why sus chords exist: the tension-and-release trick

A sus chord almost never sits still for long. Its entire purpose is to create a moment of tension that your ear expects to resolve, and then either resolve it back to the plain major chord or move it somewhere else entirely. The most common use of Gsus4 specifically is right before or after a plain G chord, so the 3rd is pulled out and then put back in, which is audible as a little lift or "catch" in the strum even if the listener could not name what changed. "Hey There Delilah" by Plain White T's is a widely tabbed example that moves through Gsus4 alongside Dsus4 in exactly this way, using the suspended chords as connective tissue between the song's plain major and minor chords rather than as chords that get strummed and left alone for a full bar.

This is also why sus chords read so differently on a strummed rhythm guitar part than they do written on paper. A plain chord chart just shows "Gsus4" for a bar the same way it would show "G," giving no visual sense of motion at all, but the sound in context is closer to a brief lean rather than a destination, the guitar equivalent of leaning your weight onto your front foot before a step rather than standing still on it. Players who only ever practice chords one at a time, strummed for a full bar and then stopped before starting the next chord cold, tend to miss this entirely and need to unlearn it once they meet a sus chord for the first time, since a sus chord strummed and left alone sounds like something is unfinished, because something genuinely is.

Why Gsus4 turns up so often in worship and CCM guitar parts

If Gsus4 sounds oddly familiar the first time you learn it, it may be because contemporary worship guitar leans on it more than most other styles of popular music. The reasons are practical as much as musical: a sus4 chord is genuinely easy to add to a G-C-D-Em progression, the chord family that makes up a large share of modern worship songs, since it only asks for a small adjustment to a G shape most guitarists already know rather than a new chord entirely. It also does real harmonic work for very little effort, an open, neither-major-nor-minor sound that keeps a repeated progression from feeling like it has fully "landed" on every pass through, which suits music built around long, repeated sections more than a verse-chorus pop structure often does. None of that is unique to worship music theoretically, a G-C-D-Em song in any genre would get the same lift from the same chord, it simply turns up there often enough that many players first meet Gsus4 in exactly that context.

Changing between G and Gsus4 without losing the beat

The single biggest reason players avoid sus chords live is that they try to refret the whole shape from scratch on every change, which is slower than the song allows. The fix is to notice how little actually moves.

Comparing the open G chord (low E 3rd fret, A string 2nd fret, D and G open, B open, high E 3rd fret) to Gsus4 above, only two things change: the A string finger shifts from the 2nd fret to the 3rd fret, and a finger lands on the B string's 1st fret where nothing was fretted before. The low E and high E fingers do not move at all. Practice the change in isolation, strumming G, then sliding only the A-string finger up one fret while dropping the index finger onto the B string, back to G, over and over at a slow, steady tempo, before trying it inside a full song. Because two of your four fingers stay anchored the entire time, this change is genuinely faster to build than most beginners expect, it only feels hard the first few times because the ear is listening for a bigger difference than the hand actually has to make.

Gsus4 to C, and Gsus4 to D

Gsus4 shares two of its three notes with both C major (C, E, G) and D major (D, F#, A): it shares C and G with the C chord, and D with the D chord, which is part of why it slots naturally into progressions built around G, C, and D, one of the most common chord families in guitar music.

The standard open C chord is fretted A string 3rd fret (ring finger), D string 2nd fret (middle finger), B string 1st fret (index finger), with the low E string not played and the G and high E strings open. Comparing that to Gsus4 note for note turns up something genuinely useful: the ring finger on the A string and the index finger on the B string do not move at all, both frets, both fingers, are identical between the two chords. The only real changes are muting the low E string instead of fretting it, dropping the middle finger onto the D string's 2nd fret where it was previously resting open, and lifting the pinky off the high E string so it rings open instead of fretted. Two fingers staying completely still while a chord changes from Gsus4 to C is a bigger head start than most players expect, and it is worth deliberately noticing, since nothing in a standard chord chart points it out.

Moving from Gsus4 into D is a bigger physical shift, since the standard open D chord (D string open, G string 2nd fret, B string 3rd fret, high E string 2nd fret, with the low E and A strings not played) uses an entirely different string, the G string, that Gsus4 leaves open. The connecting thread is not a shared finger position but a shared note: the D ringing on Gsus4's open D string is the same D that anchors the entire D chord, so the low end of the sound does not lurch even though every finger on the fretting hand has to reposition. Neither move requires releasing every finger and starting over instantly, which is the same lesson as the G-to-Gsus4 change: look for the notes that already agree between the two chords, and change only what disagrees.

How Gsus4 compares to the other common open sus4 chords

Gsus4 rarely travels alone. Songs that use one open sus4 chord tend to use several, since they are built from the same idea applied to different roots, and recognizing the pattern across chords makes each new one faster to learn.

Reading down that list, the same logic repeats every time: a root note, a 5th, and a 4th standing in for the 3rd, just rearranged across whichever strings that particular chord's root sits on. A player who has Gsus4 solid and then meets Dsus4 in a song is not really learning a new concept, only a new arrangement of the same three intervals on a different set of strings, which is why it is worth treating this table as a single pattern rather than four separate chords to memorize independently.

Where Gsus sits in the key of G

In the key of G major, the chords built on each scale degree are G, Am, Bm, C, D, Em, and F#dim. Gsus4 and Gsus2 are not separate scale degrees, they are both decorations of the I chord, G itself, which is why they resolve so naturally back to plain G rather than needing to move anywhere else. That also explains why Gsus4 and Gsus2 show up constantly in the key of G specifically and far less often in keys where G is not the tonic: they are doing a job (adding motion to the home chord) that only makes sense when G is the chord the whole song is built around.

Finger independence exercises for the sticking points

Most of the buzzing and hesitation covered above traces back to two fingers, the ring finger and the pinky, not knowing how to move independently of the others. Two short drills target that directly, separate from playing the chord itself.

The first drill isolates the ring finger's move on Gsus4: with the middle finger already anchored on the low E string 3rd fret and the pinky on the high E string 3rd fret, lift only the ring finger off the A string and set it back down, over and over, without letting the other two fingers shift position at all. The second drill does the same for the pinky and the B string, alternating an open B string with the B string fretted at the 1st fret, index finger only, while the middle and ring fingers hold their positions on the outer strings. Both drills feel almost too simple to matter, but they train the exact independent motion the full chord change asks for, without the added difficulty of moving between two entire chord shapes at once. A minute on each, done slowly, tends to fix more of the buzzing described earlier than repeating the full chord change ever does on its own.

A practice routine for today

1. Fret the open Gsus4 shape from the first table above and pick each string individually, slowly, listening for any string that buzzes or goes dead. Fix that string before moving on.
2. Run the two finger independence drills above, about a minute each, before touching the full chord.
3. Strum Gsus4 four times, then Gsus2 four times, back to back, without repositioning your hand more than the A-string and B-string changes require. Repeat for two minutes.
4. Play the G-to-Gsus4-to-G change from the section above at a slow, steady 60 beats per minute, one full chord change per beat, for two full minutes before speeding up.
5. Once that change is solid, add C: G, Gsus4, G, C, in a loop, four strums per chord, and listen for how the Gsus4 note pulls toward the notes C already contains.
6. Finish by playing the barre version of Gsus4 from the moveable-shape table, even slowly and imperfectly. It trains the same finger independence the open shapes need, from a different angle.

Five to ten minutes of this, done daily, is enough to make the open Gsus4 and Gsus2 shapes feel as automatic as G major itself within a couple of weeks. If a particular step still feels shaky after several days, that is a sign to spend another day on the drill behind it rather than pushing ahead to the next one, the routine is ordered so each step depends on the one before it.

Common mistakes beginners make with sus chords

Strumming a sus chord like it is the destination, not a stop along the way

Because sus chords are unresolved by design, holding one for a long, sustained strum without moving on can sound unfinished in a way that feels like a mistake even when every note is correct. Most uses of Gsus4 and Gsus2 in real songs pass through quickly, often for less than a full bar, before resolving.

Confusing Gsus2 and Gsus4 by ear and fixing the wrong string

Since both chords share four of six strings, a player who hears something is "off" will sometimes adjust the wrong finger, for example muting the A string on Gsus4 by mistake and assuming they meant to play Gsus2. Check the shape against the table, not against a guess, before changing anything.

Adding the 3rd back in by accident

A finger that drifts slightly and brushes the open B string on Gsus4, letting B (the 3rd) ring alongside the C, cancels out the entire suspended effect. Since the whole identity of a sus chord is the absence of the 3rd, this is the one wrong note that matters most.

Treating the barre version as a substitute for learning the open shape first

The moveable barre version further up the neck produces the identical notes as the open Gsus4 shape, but it demands more finger independence to fret cleanly. Players who try to skip straight to the barre version before the open shape is solid tend to get a muted, half-formed chord in both places.

Never actually resolving the suspension in practice

Since Gsus4 is built to lead somewhere, practicing it only in isolation, strummed on its own with nothing before or after it, skips the part that makes it worth learning. It is worth always practicing Gsus4 attached to at least one other chord, usually G, so the ear gets used to hearing the tension and its release as a single musical idea rather than two unrelated chords.

Frequently asked questions

Is Gsus the same as Gsus4?

Written on its own with nothing after it, "Gsus" is understood by convention to mean Gsus4, not Gsus2. If a chord chart wants the other version it will write "Gsus2" explicitly.

Does Gsus4 always resolve to G?

Not always, but it does so most often. Because Gsus4 shares two notes with both C and D as well, it can resolve to either of those chords instead of back to plain G, depending on where the songwriter wants the tension to land.

Why does Gsus4 sound unfinished even when I am playing it correctly?

That unfinished quality is the entire point of a suspended chord, it is not a sign anything is wrong with your fingering. The 3rd, the note responsible for a chord sounding "resolved," has been deliberately removed.

Can I play Gsus4 with a capo instead of the open shape?

A capo changes which pitch an open shape produces, it does not change which notes are missing from the chord, so the open Gsus4 shape played behind a capo is still a Gsus4 relative to the capo, just transposed. It does not replace learning the shape itself.

My high E string sounds weak on Gsus4. What should I check first?

Check the pinky first. It frets the high E string in every version of this chord and is usually the least independently controlled finger, so a weak or angled pinky is the most common cause of a thin top note.

What is the difference between Gsus4 and G7sus4?

G7sus4 adds a flat 7th, F, on top of the same G, C, D that make up Gsus4. That extra note is common in funk and soul rhythm parts and gives the chord a fuller, more harmonically busy sound than the plain sus4.

Do I need to barre anything to play Gsus4 or Gsus2?

No. Both open-position shapes in this post use only individual fingers, no barre is required unless you specifically want the moveable version further up the neck.

Which should I learn first, Gsus4 or Gsus2?

Gsus4 is the more common of the two in published chord charts and the one usually meant when a song just says "Gsus," so it is the more useful one to learn first. Gsus2 is a small adjustment away once Gsus4 is comfortable, since the two shapes share four of six strings.

Is there a two-finger version of Gsus4 I can start with?

Not one that plays all six strings cleanly, since Gsus4 needs four distinct notes across four different strings to spell out correctly. The closest genuine simplification is the four-string version further up this post that drops the low E and A strings entirely, which reduces the chord to two fingers while still keeping its correct notes.

Why do some chord charts write Gsus4 as just "Gsus" and others spell it out?

Both refer to the same chord by convention, the shorthand simply assumes the reader knows "sus" defaults to sus4 unless marked otherwise. Charts aimed at more advanced players, where sus2 voicings show up more often, tend to spell out "sus4" explicitly to avoid the ambiguity altogether.

Can Gsus4 replace a plain G chord entirely in a song?

Technically yes, since nothing stops a rhythm guitar from strumming Gsus4 wherever a chart says G, but doing so through an entire song removes the contrast that makes the chord effective in the first place. Sus chords work by standing out against the plain major and minor chords around them, and a song with no plain G left to contrast against loses that effect.

Does it matter which octave the 4th appears in when I play Gsus4?

Not for the chord's identity, C is still the 4th of G whether it rings on the A string's 3rd fret or the B string's 1st fret, both appear in the open Gsus4 shape in this post. It can matter for how the chord sounds in a mix alongside other instruments, since a 4th voiced low in the chord reads as heavier and more dissonant than the same note voiced higher up, but the chord is still correctly a Gsus4 either way.

Once Gsus4 and Gsus2 feel automatic on their own, the next useful step is folding them into the chords you already know. If G major still needs work before any of this feels natural, the G minor chord and C chord posts cover two of the shapes Gsus most often sits beside, and GuitarLowKey has more chord breakdowns built the same way, one real question at a time.