Summary
Vercel launched Protected Source Maps so browser .map files return 404 to the public while staying available to authenticated team members. The feature is enabled by default for new projects and existing projects can opt in without a redeploy.
What changed
Vercel introduced Protected Source Maps to restrict production browser source maps to authenticated team access.
Why it matters
Source maps are useful for debugging but can also expose readable production code structure, filenames, and stack traces. Making protection a platform default reframes source maps as sensitive operational artifacts instead of static assets that teams have to remember to hide on their own.
Evidence excerpt
Vercel says Protected Source Maps put browser .map files behind Vercel Authentication, with new projects enabled by default and existing projects able to opt in without redeploying.