How I parse a raw WebSocket frame when debugging low-level traffic

Most WebSocket debugging happens at the message level, but sometimes a raw frame needs to be decoded.

I use WebSocket Frame Parser for the quick version of this task, then I review the output before relying on it.

The simple idea

Most WebSocket debugging happens at the message level, but sometimes a raw frame needs to be decoded.

The tool is a shortcut for the mechanical work. It does not remove the need to understand what the result means.

Step 1: Paste the frame bytes as hex

Paste the frame bytes as hex.

Step 2: Read the opcode

Read the opcode.

Step 3: Check whether the frame is masked

Check whether the frame is masked.

Step 4: Review payload length

Review payload length.

Step 5: Decode text payloads when possible

Decode text payloads when possible.

Step 6: Do not confuse frames with full application messages

Do not confuse frames with full application messages.

Step 7: Use higher-level WebSocket tools unless frame-level debugging is necessary

Use higher-level WebSocket tools unless frame-level debugging is necessary.

My checklist

Before I trust the result, I check:

• Paste the frame bytes as hex.
• Read the opcode.
• Check whether the frame is masked.
• Review payload length.
• Decode text payloads when possible.
• Do not confuse frames with full application messages.
• Use higher-level WebSocket tools unless frame-level debugging is necessary.

That review step is what keeps a quick tool from becoming a quick mistake.