About WebSocket Frame Decoder

Decode WebSocket frame headers and payloads from hex. Part of the DevTools Surf developer suite. Browse more tools in the Networking collection.

Use Cases

• Debugging WebSocket frame encoding in real-time applications
• Analyzing raw WebSocket traffic captured from network inspectors
• Verifying correct frame masking in custom WebSocket implementations
• Inspecting binary protocol messages in IoT device communication

Tips

• Paste hex-encoded frame data to decode headers and payload
• Identify opcode to determine if the frame is text or binary
• Check masking bit to verify client-to-server frame compliance

Fun Facts

• The WebSocket protocol (RFC 6455) was standardized in December 2011 after 3 years of development to replace long-polling techniques.
• WebSocket frames have a minimum overhead of just 2 bytes for small payloads, compared to HTTP's typical 700+ bytes of headers per request.
• The masking requirement for client-to-server frames was added to prevent cache poisoning attacks on transparent HTTP proxies.

FAQ

What does it decode?

WebSocket frame header (opcode, FIN, mask, length) plus the payload. Useful for debugging WS-level issues that browser DevTools don't expose.

What are the opcodes?

0x1 (text), 0x2 (binary), 0x8 (close), 0x9 (ping), 0xA (pong), 0x0 (continuation). The tool explains each as it decodes.

Is the mask always set?

For client-to-server frames, yes — required by the protocol (RFC 6455). Server-to-client frames must NOT be masked.

Can I encode a frame?

No — this tool decodes received data. For testing WS servers, use a real WS client (wscat, browser DevTools, or Postman's WebSocket feature).