Custom Header Naming Convention in HTTP: Best Practices and Conventions

HTTP headers are the unsung heroes of web communication, carrying crucial metadata that powers everything from authentication to caching. While standard headers like Content-Type and Authorization are well-established, modern applications often require custom headers to transmit application-specific data. But here’s the challenge: poor header naming can break APIs, confuse developers, and create security vulnerabilities.

In 2025, with the rise of microservices, GraphQL, and edge computing, proper header naming has become more critical than ever. This comprehensive guide explores modern HTTP header naming conventions, the evolution beyond the deprecated “X-“ prefix, and battle-tested practices from leading tech companies.

Whether you’re building REST APIs, implementing middleware, or designing distributed systems, mastering header naming conventions will make your applications more maintainable, secure, and interoperable.

Understanding HTTP Header Architecture
Current HTTP Specifications and Standards
Modern Custom Header Naming Strategies
The X- Prefix: History and Deprecation
Industry Best Practices and Real-World Examples
Security Considerations in Header Design
Implementation Guidelines and Code Examples
Common Pitfalls and How to Avoid Them

Understanding HTTP Header Architecture

The Foundation of Web Communication

HTTP headers are name-value pairs that provide essential metadata about requests and responses. They enable features like content negotiation, caching, authentication, and cross-origin resource sharing (CORS). Understanding their structure is crucial for designing effective custom headers.

Header anatomy:

Header-Name: Header-Value
Content-Type: application/json
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
X-Custom-Header: custom-value

Types of HTTP Headers

Standard Headers: Defined by IANA and various RFCs

Content-Type, Authorization, Cache-Control
Universally recognized across all HTTP implementations

Provisional Headers: Experimental or pending standardization

May become standard or deprecated over time
Require careful consideration before adoption

Custom Headers: Application-specific extensions

Used for proprietary functionality
Must avoid conflicts with existing and future standards

Header Processing in Modern Infrastructure

Modern web applications involve complex infrastructure where headers pass through multiple layers:

Client → CDN → Load Balancer → API Gateway → Microservice

Each layer may:

Modify headers: Add security headers, remove sensitive data
Validate headers: Check size limits, character restrictions
Route requests: Based on custom header values
Log headers: For monitoring and debugging

Critical considerations:

Case sensitivity: While HTTP/1.1 headers are case-insensitive, HTTP/2 requires lowercase
Size limits: Many proxies limit header size (8KB typical maximum)
Character encoding: ASCII is safest; UTF-8 requires careful handling
Security implications: Headers can leak sensitive information

Current HTTP Specifications and Standards

Evolution from RFC 2616 to Modern Standards

While the original article referenced RFC 2616 (1999), the HTTP specification has evolved significantly. Current standards include:

RFC 7230-7237 (HTTP/1.1, 2014):

Replaced RFC 2616 with more precise definitions
Clarified header field parsing and validation
Enhanced security considerations

RFC 7540 (HTTP/2, 2015):

Introduced binary framing and header compression
Required lowercase header names for HTTP/2
Maintained semantic compatibility with HTTP/1.1

RFC 9114 (HTTP/3, 2022):

Built on QUIC transport protocol
Preserved HTTP/2 header semantics
Enhanced security and performance

Header Name Syntax Rules

Valid characters for header names:

header-name = token
token = 1*tchar
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
        "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA

Invalid characters:

Control characters (0-31, 127)
Separators: ()[]{}@,;:\"/=?<> \t
Unicode/non-ASCII characters

Header value constraints:

May contain any printable ASCII characters
Leading/trailing whitespace is trimmed
Line folding (obsolete in HTTP/1.1+)

HTTP/2 and HTTP/3 Specific Requirements

Mandatory lowercase: All header names must be lowercase

# ✅ Valid in HTTP/2/3
content-type: application/json
x-api-key: abc123

# ❌ Invalid in HTTP/2/3
Content-Type: application/json
X-API-Key: abc123

Pseudo-headers: Special headers starting with : (reserved for protocol use)

:method: GET
:path: /api/users
:authority: api.example.com

Security and Privacy Considerations

Modern HTTP specifications emphasize security:

RFC 6265 (Cookies):

SameSite, Secure, HttpOnly attributes
Affects how custom headers interact with cookies

RFC 7034 (X-Frame-Options):

Example of widely-adopted custom header that became standard

Privacy implications:

Headers can fingerprint users and leak sensitive data
GDPR and privacy regulations affect header design choices

Modern Custom Header Naming Strategies

The Post-X- Era Approach

Since RFC 6648 (2012) deprecated the “X-“ prefix, modern header naming focuses on meaningful, conflict-resistant names. Here are the current best practices:

1. Organization/Application Prefix Strategy

Format: {Organization}-{Purpose}-{Specifics}

# Company-specific headers
GitHub-Media-Type: github.v3+json
Stripe-Version: 2020-08-27
Shopify-Shop-Domain: mystore.myshopify.com

# Application-specific headers
MyApp-Request-ID: 550e8400-e29b-41d4-a716-446655440000
MyApp-User-Role: admin
MyApp-Feature-Flags: dark-mode,beta-features

Advantages:

Clear ownership and scope
Minimal collision risk
Easy to filter in logs and monitoring

2. Functional Domain Prefixes

Format: {Domain}-{Function}

# Authentication domain
Auth-Token: bearer-token-here
Auth-Provider: oauth2-google
Auth-Scope: read,write

# Rate limiting domain
Rate-Limit: 1000
Rate-Remaining: 742
Rate-Reset: 2024-08-10T15:30:00Z

# Tracing domain
Trace-ID: 4bf92f3577b34da6a3ce929d0e0e4736
Span-ID: 00f067aa0ba902b7

3. Reverse Domain Convention

Format: {ReverseDomain}-{Function}

# Based on domain ownership
Com-Example-API-Version: v2
Org-Apache-Request-ID: req-12345
Io-Kubernetes-Pod-Name: web-pod-abc123

4. Camel Case vs Kebab Case

Kebab-case (recommended):

Content-Security-Policy: default-src 'self'
X-Frame-Options: DENY
Access-Control-Allow-Origin: *

PascalCase (alternative):

MyApp-RequestId: 12345
GitHub-MediaType: application/json

Why kebab-case is preferred:

Consistent with existing HTTP standards
Better readability in logs
Compatible with HTTP/2 lowercase requirement

5. Semantic Naming Patterns

Action-based naming:

# What the header does
Enable-Debug-Mode: true
Skip-Cache: true
Force-Refresh: true

Data-type based naming:

# What type of data it contains
Request-Timestamp: 2024-08-10T12:00:00Z
User-Agent-Hash: sha256:abc123...
Session-Token: encrypted-token-here

6. Modern Industry Patterns

OpenTelemetry standard:

traceparent: 00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01
tracestate: rojo=00f067aa0ba902b7,congo=t61rcWkgMzE

Cloud provider patterns:

# AWS
X-Amz-Request-ID: 1234567890ABCDEF
X-Amz-Date: 20230810T120000Z

# Google Cloud
X-Goog-Request-ID: request-id-12345
X-Goog-User-Project: my-project-id

# Microsoft Azure
X-Ms-Request-ID: correlation-id-12345
X-Ms-Version: 2021-04-10

Header Lifecycle Management

Development stages:

Experimental: MyApp-Experimental-Feature
Beta: MyApp-Beta-NewAPI
Stable: MyApp-NewAPI
Deprecated: Add deprecation warnings

Versioning strategy:

# Version in header name (not recommended)
MyApp-V1-Token: legacy-token
MyApp-V2-Token: new-token

# Version in header value (recommended)
MyApp-API-Version: v2
MyApp-Token: new-token-format

The X- Prefix: History and Deprecation

Historical Context and Original Purpose

The “X-“ prefix convention originated in the 1980s across various internet protocols, not just HTTP. It was designed to:

Indicate experimental status: Mark headers as non-standard extensions
Prevent namespace collision: Avoid conflicts with future standards
Enable innovation: Allow vendors to experiment safely

Timeline of X- Headers

Early adoption (1990s-2000s):

X-Forwarded-For: 192.168.1.1
X-Real-IP: 10.0.0.1
X-Requested-With: XMLHttpRequest

Peak usage (2000s-2010s):

X-Frame-Options: DENY
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
X-Powered-By: Express

The Deprecation: RFC 6648 (2012)

RFC 6648 “Deprecating the ‘X-‘ Prefix” identified critical problems:

Problem 1: Standardization challenges

# Before: Experimental header
X-Frame-Options: DENY

# After: Became widely adopted but kept the X-
# Should have become: Frame-Options: DENY
# But changing would break existing implementations

Problem 2: Permanent experimental status

Headers remained “experimental” despite widespread adoption
Created confusion about stability and support

Problem 3: Inconsistent implementation

Different vendors implemented same concepts with different X- names
Led to fragmentation instead of interoperability

Modern Migration Strategies

For existing X- headers:

# Legacy support (maintain compatibility)
X-API-Key: legacy-key-here
API-Key: legacy-key-here

# Gradual deprecation with warnings
X-Old-Header: value
Warning: "X-Old-Header is deprecated, use New-Header instead"
New-Header: value

Version-based migration:

# API v1 (legacy)
X-MyApp-Token: old-format

# API v2 (modern)
MyApp-Authorization: Bearer new-format

When X- Headers Are Still Acceptable

Development and testing:

# Clearly temporary/internal use
X-Debug-Mode: true
X-Test-Environment: staging
X-Internal-Request-ID: dev-12345

Rapid prototyping:

# Short-term experimental features
X-Prototype-Feature: alpha-testing
X-Experimental-API: beta-version

Legacy X- Headers That Became Standards

Some X- headers were so successful they influenced official standards:

Security headers:

X-Frame-Options → Content-Security-Policy: frame-ancestors
X-Content-Type-Options → Part of Fetch specification
X-XSS-Protection → Superseded by CSP

Forwarding headers:

X-Forwarded-For → Forwarded header (RFC 7239)
X-Forwarded-Proto → Forwarded: proto= parameter

Best Practices for X- Migration

1. Audit existing X- headers

# Find all X- headers in your codebase
grep -r "X-" /path/to/project --include="*.js" --include="*.py"

2. Create migration timeline

// Example deprecation strategy
const DEPRECATED_HEADERS = {
  "X-API-Key": "Authorization",
  "X-Request-ID": "Request-ID",
  "X-User-Role": "User-Role"
};

function handleDeprecatedHeaders(req, res, next) {
  Object.entries(DEPRECATED_HEADERS).forEach(([old, new_]) => {
    if (req.headers[old.toLowerCase()]) {
      // Support old header temporarily
      req.headers[new_.toLowerCase()] = req.headers[old.toLowerCase()];

      // Add deprecation warning
      res.setHeader(
        "Warning",
        `299 - "Header ${old} is deprecated, use ${new_}"`
      );
    }
  });
  next();
}

3. Documentation and communication

## Header Migration Guide

### Deprecated Headers (Remove by 2025-12-31)

- `X-API-Key` → Use `Authorization: Bearer <token>`
- `X-Request-ID` → Use `Request-ID`

### Migration Steps

1. Update client code to use new headers
2. Test with both old and new headers
3. Remove old header usage
4. Server will stop accepting old headers after deprecation date

Industry Best Practices and Real-World Examples

Enterprise-Grade Header Strategies

Authentication and Authorization:

# Modern OAuth 2.0 / JWT approach
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...

# API key authentication
API-Key: sk_live_4eC39HqLyjWDarjtT1zdp7dc
MyApp-API-Key: app_12345_abcdef

# Multi-tenant authentication
Tenant-ID: acme-corp
Organization-Context: org_xyz789

Request Tracking and Observability:

# Distributed tracing (OpenTelemetry standard)
traceparent: 00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01
tracestate: rojo=00f067aa0ba902b7,congo=t61rcWkgMzE

# Custom request tracking
Request-ID: req_2VaJDRu8BV9JQg
Correlation-ID: corr_98765
MyApp-Session-ID: sess_abc123def456

Feature Flags and Versioning:

# API versioning
API-Version: 2023-08-10
Accept-Version: v2
MyApp-Schema-Version: 1.2.3

# Feature flags
Feature-Flags: dark-mode,beta-ui,new-checkout
MyApp-Experiments: experiment-a,experiment-b
Enable-Beta-Features: true

Rate Limiting and Performance:

# Rate limiting information
Rate-Limit-Limit: 1000
Rate-Limit-Remaining: 742
Rate-Limit-Reset: 2024-08-10T15:30:00Z
Rate-Limit-Policy: 1000;w=3600

# Performance hints
Cache-Preference: no-cache
Response-Timeout: 30s
Priority: high

Technology Company Examples

GitHub’s approach:

# Clear, functional naming
GitHub-Media-Type: github.v3+json
GitHub-Request-ID: 1234:5678:9ABC:DEF0
GitHub-Enterprise-Version: 3.1.0

# Feature-specific headers
GitHub-Supported-Oauth-Scopes: repo, user
GitHub-OAuth-Scopes: repo

Stripe’s strategy:

# Version-based approach
Stripe-Version: 2020-08-27
Stripe-Account: acct_12345
Stripe-Should-Retry: false

# Idempotency for financial operations
Idempotency-Key: unique-operation-id-12345

Shopify’s pattern:

# Multi-tenant e-commerce
Shopify-Shop-Domain: mystore.myshopify.com
Shopify-Access-Token: shpat_abc123
Shopify-API-Version: 2023-07

Domain-Specific Naming Patterns

E-commerce applications:

# Shopping cart context
Cart-ID: cart_abc123
Session-Currency: USD
Customer-Segment: premium
Pricing-Region: us-west

# Inventory management
Warehouse-Location: us-east-1
Stock-Check-Required: true

Financial services:

# Compliance and audit
Transaction-ID: txn_abc123def456
Audit-User-ID: user_98765
Compliance-Region: EU
Regulation-Context: gdpr,pci-dss

# Risk management
Risk-Score: 0.75
Fraud-Check-Required: true

Healthcare applications:

# HIPAA compliance
Patient-Context-ID: ctx_encrypted_abc123
PHI-Access-Level: restricted
Audit-Log-Required: true
HIPAA-Compliance-Mode: strict

Progressive Web App (PWA) Headers

# Service worker related
SW-Update-Available: true
SW-Version: v2.1.0
Offline-Capability: full

# Performance optimization
Resource-Priority: critical
Preload-Strategy: aggressive
Cache-Strategy: cache-first

Security Considerations in Header Design

Information Disclosure Risks

Sensitive data exposure:

# ❌ BAD: Exposing sensitive information
Debug-User-Data: {"email":"[email protected]","role":"admin"}
Internal-Server-Path: /var/www/app/private/
Database-Query: SELECT * FROM users WHERE id=123

# ✅ GOOD: Safe debug information
Debug-Request-ID: req_abc123
Debug-Trace-Enabled: true
Debug-Level: info

Server fingerprinting:

# ❌ BAD: Revealing infrastructure details
X-Powered-By: Node.js v16.14.0
Server-Instance-ID: prod-server-42
Internal-Service-Version: user-service-v1.2.3

# ✅ GOOD: Generic or no information
X-Request-ID: req_abc123
# Remove X-Powered-By entirely

CORS and Cross-Origin Considerations

Custom headers and CORS:

// Headers that trigger preflight requests
const NON_SIMPLE_HEADERS = [
  "Authorization",
  "Content-Type: application/json",
  "X-Custom-Header",
  "API-Key"
];

// CORS configuration for custom headers
app.use(
  cors({
    exposedHeaders: ["Request-ID", "Rate-Limit-Remaining", "MyApp-Version"],
    allowedHeaders: [
      "Content-Type",
      "Authorization",
      "API-Key",
      "MyApp-Client-Version"
    ]
  })
);

Security Header Integration

Content Security Policy considerations:

# Nonce-based CSP with custom headers
Content-Security-Policy: script-src 'nonce-{request-id}'
Request-ID: req_abc123_def456
CSP-Nonce: req_abc123_def456

Authentication security:

# Secure token handling
Authorization: Bearer <token>
Token-Expiry: 2024-08-10T15:30:00Z
Refresh-Required: false

# Avoid exposing tokens in custom headers
# ❌ BAD
Custom-Auth-Token: sensitive-token-here

# ✅ GOOD: Use standard Authorization header
Authorization: Bearer <token>

Implementation Guidelines and Code Examples

Node.js/Express Implementation

// Middleware for custom header handling
const customHeaderMiddleware = (req, res, next) => {
  // Generate request ID
  const requestId = `req_${Date.now()}_${Math.random()
    .toString(36)
    .substr(2, 9)}`;
  req.requestId = requestId;
  res.setHeader("Request-ID", requestId);

  // API versioning
  const apiVersion = req.headers["api-version"] || "v1";
  req.apiVersion = apiVersion;
  res.setHeader("API-Version", apiVersion);

  // Rate limiting headers
  const rateLimit = getRateLimit(req.ip);
  res.setHeader("Rate-Limit-Limit", rateLimit.total);
  res.setHeader("Rate-Limit-Remaining", rateLimit.remaining);
  res.setHeader("Rate-Limit-Reset", rateLimit.resetTime);

  next();
};

// Header validation middleware
const validateCustomHeaders = (req, res, next) => {
  const requiredHeaders = ["API-Key", "User-Agent"];
  const missingHeaders = requiredHeaders.filter(
    (header) => !req.headers[header.toLowerCase()]
  );

  if (missingHeaders.length > 0) {
    return res.status(400).json({
      error: "Missing required headers",
      missing: missingHeaders
    });
  }

  // Validate API key format
  const apiKey = req.headers["api-key"];
  if (apiKey && !apiKey.match(/^sk_[a-z]+_[A-Za-z0-9]{24}$/)) {
    return res.status(400).json({
      error: "Invalid API key format"
    });
  }

  next();
};

Python/FastAPI Implementation

from fastapi import FastAPI, Header, HTTPException, Request
from typing import Optional
import uuid
import time

app = FastAPI()

@app.middleware("http")
async def add_custom_headers(request: Request, call_next):
    # Generate request ID
    request_id = f"req_{int(time.time())}_{str(uuid.uuid4())[:8]}"

    # Process request
    response = await call_next(request)

    # Add custom response headers
    response.headers["Request-ID"] = request_id
    response.headers["API-Version"] = "v1"
    response.headers["Server-Time"] = str(int(time.time()))

    return response

@app.get("/api/users")
async def get_users(
    api_key: str = Header(..., description="API key for authentication"),
    user_agent: str = Header(..., description="Client user agent"),
    request_id: Optional[str] = Header(None, description="Client request ID"),
    feature_flags: Optional[str] = Header(None, description="Comma-separated feature flags")
):
    # Validate API key
    if not api_key.startswith("sk_"):
        raise HTTPException(status_code=401, detail="Invalid API key format")

    # Process feature flags
    enabled_features = []
    if feature_flags:
        enabled_features = [f.strip() for f in feature_flags.split(",")]

    return {
        "users": [],
        "request_id": request_id,
        "features": enabled_features
    }

Go Implementation

package main

import (
    "fmt"
    "net/http"
    "strings"
    "time"
    "github.com/google/uuid"
)

// Custom header middleware
func customHeaderMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Generate request ID
        requestID := fmt.Sprintf("req_%d_%s",
            time.Now().Unix(),
            strings.ReplaceAll(uuid.New().String(), "-", "")[:8])

        // Set response headers
        w.Header().Set("Request-ID", requestID)
        w.Header().Set("API-Version", "v1")
        w.Header().Set("Server-Time", fmt.Sprintf("%d", time.Now().Unix()))

        // Add request ID to context
        r.Header.Set("X-Internal-Request-ID", requestID)

        next.ServeHTTP(w, r)
    })
}

// Header validation middleware
func validateHeaders(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Check required headers
        apiKey := r.Header.Get("API-Key")
        if apiKey == "" {
            http.Error(w, "API-Key header required", http.StatusBadRequest)
            return
        }

        // Validate API key format
        if !strings.HasPrefix(apiKey, "sk_") {
            http.Error(w, "Invalid API key format", http.StatusUnauthorized)
            return
        }

        next.ServeHTTP(w, r)
    })
}

func main() {
    mux := http.NewServeMux()

    // Apply middleware
    handler := customHeaderMiddleware(validateHeaders(mux))

    http.ListenAndServe(":8080", handler)
}

Common Pitfalls and How to Avoid Them

Case Sensitivity Issues

Problem: Inconsistent header name casing across HTTP versions

// ❌ BAD: Case-sensitive handling
if (req.headers["Content-Type"]) {
  /* HTTP/1.1 */
}
if (req.headers["content-type"]) {
  /* HTTP/2 */
}

// ✅ GOOD: Always use lowercase
const contentType = req.headers["content-type"] || req.headers["Content-Type"]; // Fallback for HTTP/1.1

// ✅ BETTER: Use framework helpers
const contentType = req.get("Content-Type"); // Express.js

Header Size Limitations

Problem: Headers exceeding proxy/server limits

// ❌ BAD: Large headers
res.setHeader("User-Permissions", JSON.stringify(largePermissionsObject));
res.setHeader("Debug-Data", JSON.stringify(debugInfo));

// ✅ GOOD: Compact headers
res.setHeader("User-Role", "admin");
res.setHeader("Debug-Level", "info");
// Use response body for large data

Security Anti-patterns

Problem: Exposing sensitive information

// ❌ BAD: Sensitive data in headers
res.setHeader("User-Password-Hash", userHash);
res.setHeader("Database-Connection", dbConnectionString);
res.setHeader("Internal-API-Keys", apiKeys.join(","));

// ✅ GOOD: Safe debugging information
res.setHeader("Request-ID", requestId);
res.setHeader("Processing-Time", `${processingTime}ms`);
res.setHeader("Cache-Status", "hit");

Performance Impact

Problem: Too many custom headers affecting performance

// ❌ BAD: Header proliferation
res.setHeader("Feature-A-Enabled", "true");
res.setHeader("Feature-B-Enabled", "false");
res.setHeader("Feature-C-Enabled", "true");
// ... 50 more feature flags

// ✅ GOOD: Compact representation
res.setHeader("Feature-Flags", "feature-a,feature-c");
res.setHeader("Features-Version", "v2.1.0");

CORS Complexity

Problem: Custom headers requiring preflight requests

// ❌ BAD: Many custom headers
axios.get("/api/data", {
  headers: {
    "X-Custom-Auth": token,
    "X-User-Role": role,
    "X-Request-Source": "web-app",
    "X-Feature-Flags": flags
  }
}); // Triggers CORS preflight

// ✅ GOOD: Minimize custom headers
axios.get("/api/data", {
  headers: {
    Authorization: `Bearer ${token}`,
    "X-Client-Context": JSON.stringify({ role, source: "web", flags })
  }
});

Comprehensive Best Practices Summary

Header Design Principles

Clarity over brevity: Request-ID is better than RID
Consistency: Use the same pattern across your entire application
Future-proofing: Avoid patterns that might conflict with future standards
Security-first: Never expose sensitive data in headers
Performance awareness: Consider the cumulative size of all headers

Naming Convention Checklist

Migration Strategy

Audit existing headers in your application
Plan migration timeline for X- prefixed headers
Implement dual support during transition periods
Monitor usage and performance impact
Communicate changes to API consumers
Update documentation and examples
Remove deprecated headers after sunset period

Conclusion: Building Future-Ready HTTP APIs

Custom HTTP headers remain a powerful tool for building sophisticated web applications and APIs. The key to success lies in following modern conventions, prioritizing security and performance, and designing for long-term maintainability.

As we move further into the era of HTTP/3, edge computing, and microservices, proper header design becomes even more critical. The practices outlined in this guide will help you build APIs that are not only functional today but remain compatible and maintainable as web standards continue to evolve.

Key takeaways for 2025 and beyond:

Abandon X- prefixes for new headers while gracefully migrating existing ones
Use meaningful, organization-prefixed names to avoid conflicts
Design for HTTP/2 and HTTP/3 with lowercase naming
Prioritize security and avoid exposing sensitive information
Plan for observability with proper request tracking headers
Consider performance implications of header proliferation
Document thoroughly and communicate changes clearly

The future of web development relies on interoperable, secure, and performant protocols. By following these modern header naming conventions, you’re contributing to a better web for everyone.

Updated References and Standards

HTTP/1.1 Message Syntax and Routing (RFC 7230): Current HTTP/1.1 specification
- RFC 7230 - HTTP/1.1 Message Syntax and Routing
HTTP/1.1 Semantics and Content (RFC 7231): HTTP methods, status codes, and headers
- RFC 7231 - HTTP/1.1 Semantics and Content
Deprecating the “X-“ Prefix (RFC 6648): Official deprecation of X- prefix
- RFC 6648 - Deprecating the X- Prefix
HTTP/2 Specification (RFC 7540): Binary protocol with mandatory lowercase headers
- RFC 7540 - Hypertext Transfer Protocol Version 2 (HTTP/2)
HTTP/3 Specification (RFC 9114): Latest HTTP version over QUIC
- RFC 9114 - HTTP/3
IANA Message Headers Registry: Official registry of HTTP header fields
- HTTP Header Field Definitions
MDN HTTP Headers Documentation: Comprehensive developer resource
- HTTP Headers - MDN Web Docs
OpenTelemetry Specification: Modern observability standards
- OpenTelemetry HTTP Semantic Conventions
OWASP Security Headers: Security best practices for HTTP headers
- OWASP Secure Headers Project

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