HTTP 431 Error Analysis and Solutions

In daily website development and API debugging, we often encounter various HTTP status codes. Among them, HTTP 431 Request Header Fields Too Large is a relatively rare error but can significantly impact request processing. This article will walk you through the definition of HTTP 431, common causes, and troubleshooting strategies.

1. What is HTTP 431

HTTP 431 is a client error status code, fully named Request Header Fields Too Large. It indicates that the request header fields are too large.

When a client sends a request to the server, if a single header field or the total size of all headers exceeds the maximum limit allowed by the server, the server will return a 431 error and refuse to process the request.

Typical scenarios include:

• The browser sends an overly long Cookie
• API requests carry too many custom headers
• Redirection accumulates redundant HTTP header information

2. Common Causes of HTTP 431 Errors

Oversized Cookies

• Frequent logins, tracking data, or session information lead to excessive cookie storage
• Old data not cleared, causing large amounts of useless information to be sent with each request

Too Many Request Header Fields

• API calls include a large number of unnecessary custom headers
• Certain security plugins or proxy services automatically add extra header fields

Header Information Accumulated by Redirection

• Multiple redirects continuously append previous request headers

Low Server Configuration Limits

• Server has strict settings for RequestHeaderSize or similar parameters, making it easy to exceed limits

3. Troubleshooting and Resolving HTTP 431 Errors

Inspect and Reduce Cookies

• Use the browser developer tools to check request headers and confirm cookie size
• Remove unnecessary cookies or reduce cookie data stored on the server side

Simplify HTTP Request Headers

• Remove irrelevant custom headers
• Check whether intermediary proxies or plugins are injecting extra fields into requests

Optimize Redirect Logic

• Avoid unnecessary multiple redirects
• Ensure redirects do not repeatedly append identical headers

Adjust Server Configuration

• For Nginx, modify the large_client_header_buffers parameter
• For Apache, adjust LimitRequestFieldSize and LimitRequestFields

Use a Reliable Proxy Service

In cross-border e-commerce, ad verification, and data collection, complex request chains can easily cause header redundancy issues. Using a high-quality proxy IP service (such as CLiproxy static residential IPs) not only ensures a stable network but also reduces the injection of irrelevant headers, minimizing the likelihood of HTTP 431 errors from the source.

CLiproxy Overview and Advantages

What is CLiproxy?

CLiproxy is a trusted proxy service platform that provides global real residential, mobile, and ISP IP addresses. It supports SOCKS5, HTTP, and HTTPS protocols, suitable for automation, privacy protection, data scraping, and many other scenarios.

Key Advantages of CLiproxy

• Massive Global IP Pool
  CLiproxy offers over 100 million real residential IPs, covering more than 180 countries and regions, with city- and ISP-level targeting for global operations and regional testing.
• Unlimited Traffic & Long Connection Support
  Provides full traffic, unlimited bandwidth usage with stable long connections — ideal for long-running tasks.
• Flexible IP Rotation & Session Settings
  Supports both static and dynamic IP modes with customizable rotation intervals (e.g., every 1–60 minutes) to improve security and reduce risk.
• Competitive Pricing
  Offers industry-leading rates, supports both IP- and traffic-based billing, and provides non-expiring data packages for high cost-effectiveness.
• High Anonymity & Reliability
  All IPs are sourced from real residential networks, making them stable and hard to detect as proxies — perfect for risk-sensitive scenarios.
• Wide Protocol & Platform Compatibility
  Compatible with HTTP, HTTPS, SOCKS5; supports Windows, macOS, and Linux; integrates seamlessly with crawler tools and multi-account browsers.
• Multiple IP Acquisition Methods & Excellent Support
  Offers Web, API, and client-based IP extraction with 24/7 customer support to help users deploy and troubleshoot quickly.

Common Use Cases

• Data scraping / web crawling
• Ad and content regional testing
• Cross-border e-commerce / bulk social media account management
• SEO / SERP analysis
• Market research / price monitoring
• Automated testing and multi-account management

CLiproxy delivers stable, efficient, secure, and cost-effective proxy solutions for these scenarios, especially where high concurrency, high anonymity, and broad geographic coverage are needed.

📌 If your business requires such capabilities, you can contact CLiproxy’s online support here: https://t.me/cliproxy

Summary

The essence of an HTTP 431 error is that request header information exceeds the limits allowed by the server. The key to resolving it lies in controlling request header size, optimizing data transmission, and properly configuring server limits. If you are performing high-frequency operations such as cross-border business or ad verification, it is recommended to combine high-quality proxy IPs to ensure network stability and reduce connection interruptions caused by oversized headers.