vercel-blob

Last Updated : 2026-01-21 Version : @vercel/blob@2.0.0 Skill Version : 2.1.0 Server Upload : CRITICAL : Never expose BLOB_READ_WRITE_TOKEN to client. Use handleUpload() for client uploads. Server Action (generates presigned token): Client Component : List/Delete : Multipart (>500MB) : Always : Never : This skill prevents 16 documented issues : Error : Error: BLOB_READ_WRITE_TOKEN is not defined Source : Why It Happens : Token not set in environment Prevention : Run vercel env pull .env.local and ensure .env.local in .gitignore . Error : Security vulnerability, unauthorized uploads Source : Why It Happens : Using BLOB_READ_WRITE_TOKEN directly in client code Prevention : Use handleUpload() to generate client-specific tokens with constraints. Error : Error: File size exceeds limit (500MB) Source : Why It Happens : Uploading file >500MB without multipart upload Prevention : Validate file size before upload, use multipart upload for large files. Error : Browser downloads file instead of displaying (e.g., PDF opens as text) Source : Production debugging Why It Happens : Not setting contentType option, Blob guesses incorrectly Prevention : Always set contentType: file.type or explicit MIME type. Error : Slow file delivery, high egress costs Source : Vercel Blob best practices Why It Happens : Using access: 'private' for files that should be public Prevention : Use access: 'public'...