RFC 7541 - HPACK: Header Compression for HTTP/2

• Status: Proposed Standard
• Published: May 2015
• Stream: IETF
• Errata: No Errata

---

Abstract

This specification defines HPACK, a compression format for efficiently representing HTTP header fields, to be used in HTTP/2.

---

Table of Contents

• 1. Introduction
  • 1.1 Overview
  • 1.2 Conventions
  • 1.3 Terminology
• 2. Compression Process Overview
  • 2.1 Header List Ordering
  • 2.2 Encoding and Decoding Contexts
  • 2.3 Indexing Tables
  • 2.4 Header Field Representation
• 3. Header Block Decoding
  • 3.1 Header Block Processing
  • 3.2 Header Field Representation Processing
• 4. Dynamic Table Management
  • 4.1 Calculating Table Size
  • 4.2 Maximum Table Size
  • 4.3 Entry Eviction When Dynamic Table Size Changes
  • 4.4 Entry Eviction When Adding New Entries
• 5. Primitive Type Representations
  • 5.1 Integer Representation
  • 5.2 String Literal Representation
• 6. Binary Format
  • 6.1 Indexed Header Field Representation
  • 6.2 Literal Header Field Representation
  • 6.3 Dynamic Table Size Update
• 7. Security Considerations
  • 7.1 Probing Dynamic Table State
  • 7.2 Static Huffman Encoding
  • 7.3 Memory Consumption
  • 7.4 Implementation Limits

Appendices

• Appendix A. Static Table Definition
• Appendix B. Huffman Code

---

Related Resources

• Official Text: RFC 7541
• Official Page: RFC 7541 DataTracker
• Errata: RFC Editor Errata

---