413 Content Too Large (formerly Payload Too Large) tells the client the request body is bigger than the server is willing to accept. Common limits: 1MB for JSON APIs, 10-100MB for file uploads, multi-GB for object storage. The response should include a Retry-After header (rare but spec-allowed) and ideally a body explaining the limit. Note: the older spec name "Payload Too Large" is still used in many libraries and tools.
When servers should return it: Return 413 when the request body exceeds the configured maximum.
Common causes
File upload exceeds server limit
Bulk import payload too large
JSON body has too many items in an array
CDN or proxy limit hit before reaching origin
Nginx client_max_body_size or equivalent exceeded
How to fix 413 Content Too Large
Split the upload into smaller chunks
Use multipart/form-data for large files instead of JSON-encoded base64
Multiple places: Nginx (client_max_body_size, default 1MB), Express (default 100KB for JSON), Cloudflare (100MB on free, more on paid), API Gateway (10MB by default).
Why is the spec name now "Content Too Large"?
RFC 9110 renamed it from "Payload Too Large" to be more accurate. Both names refer to status code 413.
Defined in: RFC 9110 · Class:4xx Client Error
More references
For a one-page reference of all HTTP status codes, see the HTTP cheat sheet. For testing API responses, try the API Tester tool. For inspecting responses on the command line, the curl cheat sheet covers the most common flags.