🔌 WebSocket Frame Decoder

What Can the WebSocket Frame Decoder Do?

The WebSocket Frame Decoder is a free online developer tool that parses WebSocket protocol binary frame data, visualizing key fields including FIN flag, Opcode type, Mask flag, Payload length, and Payload content. It supports mask decoding and automatically restores the original data sent by the client. Ideal for WebSocket protocol debugging, network packet analysis, and protocol learning. All parsing is done locally in the browser—your data is never uploaded to any server.

Core Features

• Frame Structure Parsing: Complete parsing of the WebSocket frame format defined in RFC 6455, showing each field's meaning
• Opcode Identification: Automatically recognizes text/binary/close/ping/pong and other opcode types
• Mask Decoding: Automatically detects the mask flag and uses the masking-key to XOR-decode the payload
• Multi-format Input: Supports both hexadecimal and Base64 input formats
• Consecutive Frame Parsing: Supports parsing multiple consecutive WebSocket frames

Usage Tutorial

1. Select input format (hex or Base64) and paste WebSocket frame data into the input box.

2. Click "Decode" or use the Ctrl+Enter shortcut.

3. View the detailed parsing results for each frame, including FIN, Opcode, Mask, Payload fields.

4. Click "Copy Result" to copy the parsed results or download as a JSON file.

Application Scenarios

Scenario 1: WebSocket Debugging

Developers debugging WebSocket communication can capture binary frame data and use this tool to parse frame structure and content.

Scenario 2: Protocol Learning

Students and developers learning the WebSocket protocol can understand the RFC 6455 frame format by parsing actual frame data.

Scenario 3: Network Troubleshooting

Operations teams troubleshooting WebSocket connection issues can analyze frame data to locate communication anomalies.

Extended Knowledge

The WebSocket protocol (RFC 6455) defines the basic frame format: the first byte contains the FIN flag (1 bit) and Opcode (4 bits), the second byte contains the MASK flag (1 bit) and Payload length (7 bits/16 bits/64 bits). Frames sent by the client must have MASK=1 and carry a 4-byte masking-key for XOR masking of the payload. Opcodes define frame types: 0x0=continuation, 0x1=text, 0x2=binary, 0x8=close, 0x9=ping, 0xA=pong. Payload length encoding: 126 means the next 2 bytes are the actual length, 127 means the next 8 bytes are the actual length.