VRChat's 256-bit parameter limit: how it is counted and how to find wasted bits
You add one more toggle to your avatar and Unity tells you the Expression Parameters are over budget. VRChat lets an avatar sync only a fixed amount of custom parameter data to other players, and most avatars run out because of leftovers, not because every toggle earned its place. This guide explains how the bits are counted and how to find the ones you can win back.
How the budget is counted
These figures come from VRChat's Animator Parameters page, as read on 2026-11-01.
- VRChat "can synchronize up to 256 bits of custom parameters". It also limits an avatar to 8192 custom Expression Parameters in total, synced or not.
- A Bool costs 1 bit. An Int costs 8 bits by default (values 0 to 255). A Float costs 8 bits by default.
- Only synced parameters count. A parameter that does not have Synced ticked costs nothing, and built-in parameters do not count.
- With "Show Advanced Options" ticked you can lower an Int's or a Float's bit width. The minimum is 2 bits. A smaller Int holds a smaller range, and a smaller Float is less precise.
That is 256 synced Bools, or 32 Ints or Floats, or a mix. Each Int that only ever holds 0 or 1 is eight times the cost of the Bool it could have been.
Where the waste hides
- Empty names. A blank row in the list still takes its bits if it is synced.
- Duplicates. The same name twice. VRChat syncs parameters by their position in the list, so each row takes its own bits. We have not tested how VRChat resolves the name clash.
- Parameters nothing uses. Leftovers from prefabs and outfits you removed. No animator controller, blend tree, parameter driver or menu control reads them.
- Ints used as toggles. An Int whose conditions only ever compare against 0 and 1 is a Bool candidate.
- Ints that are wider than they need to be. An outfit selector with four choices needs 2 bits, not 8.
- Parameters that do not need syncing. VRChat's page says face tracking parameters "usually do not need Synced enabled, because VRChat syncs face tracking data separately". Check yours before unticking anything.
Count it yourself
The script below takes a list written out by hand from the Inspector, with the type, the Synced box and the bit width, plus the values your animator conditions actually compare against. It totals the synced bits and lists what could be recovered. The avatar is made up.
params = [ # name, type, synced, bit width (VRChat defaults: Int and Float 8, Bool 1)
("Outfit", "int", True, 8),
("TailFluff", "int", True, 8),
("Hat", "bool", True, 1),
("Hat", "bool", True, 1),
("EarTwitch", "float", True, 8),
("OldToggle", "bool", True, 1),
("", "bool", True, 1),
("Hoodie", "bool", False, 1),
]
values_used = {"Outfit": {0, 1, 2, 3}, "TailFluff": {0, 1}} # numbers the animator compares against
nothing_reads = {"OldToggle"} # no controller, menu or driver uses it
BUDGET = 256
total = sum(bits for _, _, synced, bits in params if synced)
print(f"{total} of {BUDGET} synced bits used, {BUDGET - total} free\n")
saved, seen = 0, set()
for name, kind, synced, bits in params:
if not synced:
continue
if name == "":
print(f"(empty name): {bits} bit, remove the row")
saved += bits
elif name in seen:
print(f"{name}: listed twice, the second row costs {bits} bit, remove it")
saved += bits
elif name in nothing_reads:
print(f"{name}: nothing reads it, {bits} bit")
saved += bits
elif kind == "int" and name in values_used and max(values_used[name]) <= 1:
print(f"{name}: only ever 0 or 1, make it a Bool: saves {bits - 1} bits")
saved += bits - 1
elif kind == "int" and name in values_used and bits > 2:
need = max(2, max(values_used[name]).bit_length())
if need < bits:
print(f"{name}: values reach {max(values_used[name])}, a {need}-bit width holds that: saves {bits - need} bits")
saved += bits - need
seen.add(name)
print(f"\nrecoverable: {saved} bits, leaving {total - saved} bits used of {BUDGET}")28 of 256 synced bits used, 228 free Outfit: values reach 3, a 2-bit width holds that: saves 6 bits TailFluff: only ever 0 or 1, make it a Bool: saves 7 bits Hat: listed twice, the second row costs 1 bit, remove it OldToggle: nothing reads it, 1 bit (empty name): 1 bit, remove the row recoverable: 16 bits, leaving 12 bits used of 256
On this made-up avatar that is 28 of 256 bits used and 16 recoverable, which would leave 12 bits in use. The Hoodie Bool is not synced, so it costs nothing either way.
Before you change anything
- Back up the avatar or work in a copy of the project. Expression Parameters are an asset you can overwrite.
- Mind the order. VRChat's page says that when an avatar has both PC and Quest versions, parameters sync by their position in the list and their type, not by name, so both versions should use the same Expression Parameters asset. Deleting a row shifts everything below it. Remove rows on the shared asset, and do not let the two versions drift apart.
- Changing an Int to a Bool is not a rename. Every animator condition, menu control and parameter driver that touched it must be changed to match, or the toggle quietly stops working.
- Parameters that are read from outside Unity by OSC apps, contacts, PhysBones or constraints can look unused to a script that only reads controllers. Check before removing one.
Doing the scan inside Unity
Our own Parameter Budget Auditor does the scan from a window in the editor. You pick the avatar and press Scan, and it lists empty, duplicate and unused parameters and the Ints that only use 0 and 1, and its one-click removal can be undone with Ctrl+Z. It has limits you should know about. It counts every synced Int and Float as 8 bits, so if you have already lowered some bit widths its total will read higher than VRChat's; the lists of empty, duplicate and unused rows do not depend on that. It does not shrink bit widths or turn Ints into Bools for you. It was tested in Unity 2022.3.22f1 with VRChat Avatars SDK 3.7.6 on one test avatar, not on a wide range of real ones.
Last updated 2026-11-01. The Python on this page was run on that date and the output shown is the real output. The bit costs are from VRChat's documentation as read on that date; we have not run this in Unity or VRChat for this page.