What the error looks like
It shows up either as an nginx page or an app-level error:
<html><head><title>413 Request Entity Too Large</title></head>
# or from the app:
PayloadTooLargeError: request entity too large
at readStream (.../raw-body/index.js)Whoever enforces the limit first returns the 413. So the first question is always: did the proxy reject it, or did the app?
Why it happens
nginx client_max_body_size
Defaults to 1 MB. Any larger upload or JSON body is rejected before it reaches your app.
App body-parser limit
Express/body-parser defaults to ~100 KB for JSON. Bigger payloads throw PayloadTooLargeError.
A proxy in front of the proxy
A CDN or load balancer has its own body cap that fires before nginx or the app.
File uploads
Multipart uploads routinely exceed default limits; the upload middleware may also cap size.
Diagnose it in three steps
Find who rejects it
# Branded nginx 413 page -> it's the proxy.
# JSON/app error body -> it's your app.
tail -f /var/log/nginx/error.log # "client intended to send too large body"Raise the nginx limit
# in http, server, or the specific location block
client_max_body_size 10m;
# then: nginx -t && systemctl reload nginxRaise the app limit
app.use(express.json({ limit: '10mb' }));
app.use(express.urlencoded({ limit: '10mb', extended: true }));Set a deliberate ceiling, not infinity
Both layers must allow the size you actually need — and no more. An unbounded body limit is a denial-of-service vector. Pick a number that fits your largest legitimate upload, set it on the proxy and the app, and reject the rest fast.
# match the limits so they don't disagree:
# nginx: client_max_body_size 10m;
# express: limit '10mb'
# and stream large file uploads to disk/object storage instead of buffering.Size and rate limits in front of your app
Infraveil can put request controls in front of services on your own servers, so body-size limits can be managed consistently at the edge; you still need to set and verify the proxy and application limits.
Frequently asked questions
What causes a 413 error?
The request body exceeded a configured size limit — most often nginx's client_max_body_size (1 MB default) or your app framework's body-parser limit.
How do I fix 413 in nginx?
Set client_max_body_size to the size you need in the http, server, or location block, then test and reload: nginx -t && systemctl reload nginx.
Why do I still get 413 after raising nginx's limit?
Your application has its own limit. In Express, raise it with express.json({ limit: '10mb' }). Both the proxy and the app must allow the size.
Should I just set an unlimited body size?
No — an unbounded limit invites abuse and memory exhaustion. Set a deliberate ceiling that fits your largest legitimate request, and stream big uploads rather than buffering them.
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