Apps Script Rhino → V8 migration checklist

Google deprecated the Rhino runtime on January 31, 2026. Scripts still on Rhino are being moved to V8 — and the ones that use Rhino-only syntax stop loading. This is the full checklist, following Google's official migration guide.

1. Switch the runtime

Editor → Project Settings → check Enable Chrome V8 runtime, or set it in appsscript.json:

{
  "timeZone": "America/New_York",
  "runtimeVersion": "V8"
}

"DEPRECATED_ES5" (or no runtimeVersion on very old projects) means Rhino.

2. Fix what won't parse

Pattern	V8 error	Guide
`for each (x in y)`	Unexpected identifier 'each'	for each
`catch (e if …)`	Unexpected token 'if'	conditional catch
E4X `<xml/>`, `new XML()`, `.@id`	Unexpected token '<' / XML is not defined	E4X → XmlService
`function class()`, `var import`	Unexpected token 'class'	reserved words
reassigned `const`	Assignment to constant variable.	const
same `const` in two files	Identifier has already been declared	duplicates
`function (x) x * x`, `let (a = 1) {}`	Unexpected identifier	expression closures
`__iterator__`, `StopIteration`	StopIteration is not defined	iterators
`toSource()`, `uneval()`	toSource is not a function	toSource
`java.*`, `Packages`	java is not defined	Java bridge
`ScriptProperties`, `UiApp`, `DocsList`	ScriptProperties is not defined	legacy services

One parse error stops the whole file, so every function in it fails — even ones that look unrelated.

3. Check what behaves differently

getYear() → returns 126
toLocaleDateString() → short format
error.lineNumber → undefined
setValue(undefined), JSON.stringify(enum) → changed output
Object.keys(this), instanceof in libraries, prototype changes → globals
new Date("…") → parsing, formatDate('YYYY') → wrong year
with (…) and eval still run, but audit code strings passed to eval for Rhino-only syntax.

4. Test and redeploy

Run each trigger function from the editor; re-authorize if prompted; check Executions.
Web apps and add-ons: Deploy → Manage deployments → New version, and point every deployment at it.
Libraries: publish a new version and tell callers to update.
Standalone scripts: users need at least view access for triggers to keep working on V8.
Archive old Rhino versions/deployments.

Do it in one pass

Paste your code or upload the project zip — V8Shift scans all of the above with file and line numbers for free, and rewrites the safe fixes for you.