Description

Ensure Skew Protection is enabled for the project, so that each user's browser keeps talking to the same deployment version it first loaded, even after a new deployment goes live. This prevents the client and server from running different versions of the application during a rollout.

Rationale

When a new version is deployed, users who already have the old version open may send requests that the new server code does not understand. This version skew can cause errors, failed form submissions, broken pages, and unexpected behavior. Skew Protection locks each client to its original deployment for a period of time, making rollouts safer and more reliable.

Impact

  • Reduces errors for users during new deployments

  • Client and server stay on the same version

  • Requires the Enable access to System Environment Variables setting to be checked

Default Value

Skew Protection is a paid feature: the dashboard shows it with a Pro badge and an Upgrade button on the Hobby plan. On paid plans, it is enabled by default for projects created after November 19, 2024 that use a supported framework, and older projects must enable it manually.

Pre-Requisites

  • Team Owner or Member role, or Project Administrator

  • Pro or Enterprise plan

  • A supported framework, or code that sends the deployment ID

  • Enable access to System Environment Variables checked

  • Deployments not created with the --prebuilt option

Test Plan

  1. Sign in to Vercel at https://vercel.com.

  2. Select your team from the team switcher.

  3. Select the project from the dashboard.

  4. Open Settings in the sidebar and select Advanced.

  5. In the Skew Protection section, verify that the toggle shows Enabled.

  6. If it is disabled, follow the implementation steps.

Implementation Steps

  1. Sign in to Vercel at https://vercel.com.

  2. Select your team from the team switcher.

  3. Select the project from the dashboard.

  4. Open Settings in the sidebar, select Environments, open Production, and confirm that Enable access to System Environment Variables is checked at the bottom of the Environment Variables section.

  5. Open Settings in the sidebar and select Advanced.

  6. In the Skew Protection section, turn on the toggle, optionally set a maximum age, and save.

  7. Redeploy your latest production deployment.

Backout Plan

  1. Sign in to Vercel at https://vercel.com.

  2. Select your team from the team switcher.

  3. Select the project from the dashboard.

  4. Open Settings in the sidebar and select Advanced.

  5. In the Skew Protection section, turn off the toggle and save.

  6. Redeploy your latest production deployment.

Reference