vercel flags split configures weighted flag variants

Introduced 2026-05-19 · score 0.98

HOW TO USE IT

When configuring weighted variants for a Vercel Flag in an environment, run `vercel flags split <flag>` with the environment, bucketing attribute, and a weight for every variant. For String, Number, or JSON flags, also set the fallback variant; use `--message` to record a revision message.

WHY THIS HELPS

Configure weighted variants for a Vercel Flag in an environment during development or testing.

REQUIREMENTS AND LIMITATIONS

• Version: 54.2.0
• <flag> (required): Flag slug to configure.
• --environment, -e (required): Selects the environment for the split.
• --by (required): Selects the entity attribute used for stable bucketing, in `<entity.attribute>` form. The entity and attribute must already be defined; timestamp attributes cannot be used.
• --weight, -w (required): Use once for every variant, in `VARIANT=WEIGHT` form. Weights are normalized as ratios; `0` excludes a variant from traffic, and at least one weight must be greater than zero.
• --default-variant: For String, Number, and JSON flags, chooses the fallback served when the bucketing attribute is unavailable. Boolean splits default to `false`. Accepts a variant ID or value.
• --message: Sets an optional revision message.
• Prerequisite: Define the entity and bucketing attribute in the Vercel Flags dashboard or with `vercel flags entities` before running the command.
• Prerequisite: In non-interactive environments, pass the required split options explicitly.
• The interactive flow prompts for the environment, bucketing attribute, weights, fallback variant, and revision message.
• A variant with weight `0` is excluded from receiving traffic.

FIRST-PARTY EVIDENCE

• https://github.com/vercel/vercel/releases/tag/vercel%4054.2.0
• https://vercel.com/docs/cli/flags

Check the installed version and the source before using it. Entry JSON

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