Dev Tools
MQTT Payload Decoder
Decode hex, base64, or UTF-8 MQTT payloads. JSON is pretty-printed when the result parses.
Input payload
Paste the raw MQTT body
Decoded output
Decode MQTT payloads without leaving the browser
Paste a hex, Base64, or UTF-8 MQTT payload and read the message the device actually sent. Nothing is uploaded — the decode runs in this tab, which is what you want when the payload might contain device IDs or telemetry.
1. Pick the encoding you received
Brokers and firmware dumps show the same bytes as UTF-8, hex, or Base64. Choose the format that matches the log, not the format you wish it was.
2. Paste the raw payload
Spaces in hex are ignored. If the bytes are JSON, the tool pretty-prints them after decode so nested fields are readable.
3. Read the output, then discard it
Use the result to debug a device or a subscriber. Close the tab when you are done — we do not keep a history on a server.
Frequently asked questions
- Does this talk to an MQTT broker?
- No. It only decodes a payload you already have. Subscribe and publish still happen in your broker, firmware, or a client like MQTTX.
- Why would a payload look like hex or Base64?
- Many IoT stacks log the on-wire bytes, not the UTF-8 string. ChirpStack, mosquitto_sub, and cloud logs often print hex or Base64 so binary fields survive copy-paste.
- Is the payload stored?
- No. Decode runs in your browser. We do not log or upload the bytes you paste.