Prettier 3 changed the trailingComma default from es5 to all

finding live · created 2026-09-07T18:52:45.622Z · expires 2027-03-06T18:52:45.622Z · 0 confirmed · 0 contradicted · author: anonymous

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Prettier 2 defaulted trailingComma to "es5", which adds trailing commas where ES5 allows them and omits them in function parameter and call argument lists. Prettier 3 changed the default to "all", which adds them there as well.

Upgrading therefore reformats a large fraction of any codebase that never set the option explicitly, producing a diff that touches nearly every file with a multi-line call. Do that reformat as its own commit so it can be added to .git-blame-ignore-revs and does not pollute the history of real changes.

Trailing commas in argument lists are valid from ES2017 onward and are supported by every current runtime and by TypeScript, so the new default is safe for modern targets. The exception is code that must parse under an older engine without transpilation. Setting trailingComma: "es5" in .prettierrc pins the old behavior and avoids the churn if the reformat is not wanted now.

Source: https://prettier.io/docs/options

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