The “payload too large” or “request entity too large” error is a common HTTP status code that web developers and API users may encounter. This article will explain what this error means, why it occurs, and how to fix it.
What is the “Payload Too Large” Error?
The “payload too large” error occurs when the client sends an HTTP request with a body payload that exceeds the maximum size limit configured on the server.
Specifically, this error is signified by the HTTP status code 413 Payload Too Large. According to the HTTP specification RFC 7231:
The 413 (Payload Too Large) status code indicates that the server is refusing to process a request because the request payload is larger than the server is willing or able to process.
In other words, the server received the request but the body payload was simply too big for it to handle, so it rejected the request.
Why Does the Payload Too Large an Error Occur?
There are several reasons why this error may occur:
- The client sent more data than the server is configured to accept – Servers have maximum limits on the size of request bodies they will accept. If the client sends more data than this limit, the 413 error will occur.
- The server has lowered the request size limit – The server may have reconfigured its maximum request body size to a lower value than what the client is programmed to send. This would start resulting in 413 errors.
- There is a proxy or middleware with its own size limits – Networks may have proxy servers, load balancers, or other middleware that impose their own body size restrictions, lower than the origin server’s limit.
- The request content is too complex – For JSON or XML requests with deeply nested structures, the request size can grow quickly and exceed size limits unexpectedly.
- There is a bug in the client code sending unlimited data – Bugs may cause the client to mistakenly send arbitrarily large payloads without restriction.
So in summary, the 413 error occurs when the server is sent more data than it can or will accept according to its configuration. The client and server are mismatched in their expectations of appropriate payload sizes.
How to Fix the Payload Too Large Error
Here are some tips on how to resolve a 413 Payload Too Large error:
1. Check the server’s request size limit
Check the API documentation or server logs to determine the maximum request body size allowed. For example, Apache and Nginx have LimitRequestBody directives that impose size limits.
2. Reduce the client request data size
If possible, reduce the amount of data the client is sending in the request body. For JSON, this may involve removing unnecessary data attributes or flattening nested objects. For binary data, compress the body content using gzip or zlib to reduce its size.
3. Increase the limit on the server if appropriate
For our own servers, consider whether the request size limit can be increased to accommodate larger payloads from the client. Change the LimitRequestBody or client_max_body_size directives in the server config.
4. Add looping or pagination logic to split larger requests
For APIs that need to send large chunks of data, have the client split the data into smaller “pages” and send sequentially using pagination or looping logic. The server can then reconstruct the full body.
5. Use chunked transfer encoding
The HTTP chunked transfer encoding allows the request body to be split into smaller chunks. This avoids buffering the entire payload in memory.
6. offload payload data to external storage
Instead of sending the entire payload in the request, upload it to cloud storage like Amazon S3 and just include a reference to it in the request body.
7. Check for issues with proxies and load balancers
Some intermediate proxies or load balancers may have low body size limits. You may need to increase these limits if you have control over the network architecture.
8. Compress the request (if supported)
Enable request compression such as gzip or deflate encoding. This compresses the request body payload, reducing its transferred size. (The server must support decompression as well).
Following these tips should help diagnose and remedy request payload size issues resulting in 413 errors. The key is adjusting the server, client, or network architecture to align their expectations around request body sizes.
Best Practices for Avoiding Payload Size Limits
Here are some general best practices when dealing with request size limits:
- Avoid arbitrarily large payloads – Design APIs and clients to use appropriate payload sizes rather than trying to send maximally large amounts of data in a single request.
- Document size limits – Document maximum request and response payload sizes in your API documentation.
- Implement validation checks – On the client, validate payload size before sending requests and warn if size limits are exceeded.
- Use pagination for large data sets – Split up large responses across multiple paginated requests rather than overloaded single responses.
- Have the server handle compression – It’s best for the server to compress responses rather than clients compressing requests, as the server has more context on bandwidth.
- Set reasonable default limits – Server admins should configure appropriate default payload size limits as a fallback if limits are not specified per-resource or per-route.
- Enable chunked transfer encoding – This allows payloads streamed in smaller chunks if needed.
- Offload payload data to remote services – Rather than passing large payloads directly end-to-end, leverage cloud storage services and pass references instead.
Applying these best practices will help avoid both client-side and server-side issues around request and response payload sizes.
Troubleshooting Payload Size Issues
Here is a general methodology when troubleshooting 413 errors:
- Reproduce the error – Use debugging tools like cURL to isolate and reproduce the response in a controlled way.
- Check configured limits – Inspect server and middleware configuration for the max request body size limit setting.
- Trace the request handling – Follow the execution path on the server to see where the 413 is first triggered.
- Log payload sizes – Add payload size logging to capture exact request sizes.
- Try increasing limits – Temporarily increase limits as a test to confirm that’s the cause.
- Monitor memory usage – Pay attention to memory spikes during large requests which may indicate resource exhaustion issues.
- Test with reduced payloads – Gradually decrease payload sizes until the issues disappear.
- Check load balancer configurations – For 413 errors from intermediaries, may need to increase proxy/LB limits.
- Implement request size validation – Add client-side logic to validate sizes before sending.
With structured troubleshooting and validation, payload size errors can be quickly diagnosed and resolved.
Conclusion
The HTTP 413 Payload Too Large response indicates the server rejected the request due to excessive payload size.
Typical solutions include reducing payload amounts, increasing limits, using chunking or compression, and offloading data to external services. Following best practices around request and response sizes, documenting limits, and implementing robust validation will help avoid these errors.
Thorough troubleshooting strategies also enable resolving payload size issues promptly when they occur. Appropriately handling request and response payloads is key for robust API and web service architectures.
