How to test AT commands on a GSM/LTE modem from your browser

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AT Command Tester online - console, catalog and parsed status screenshot

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A step-by-step guide to poking a cellular module (SIMCOM, Quectel, u-blox and friends) with AT Command Tester online. (Background in the original post.)

Steps

  1. Connect the module’s serial port to your PC and open https://www.clearevo.com/at/ in Chrome or Edge (desktop, Web Serial API).
  2. Click Connect and pick the module’s port.
  3. Send commands three ways:
    • Type into the console directly.
    • Click-to-send catalog: the common commands (identity, SIM, signal, registration, operator, APN, SMS mode…) each with a one-line description - click one and it’s sent.
    • Script runner: paste a list of commands and it sends them one by one, waiting for OK/ERROR per command. Handy for repeatable module bring-up checks.
  4. Watch the parsed status panel: AT+CSQ becomes signal bars with dBm, AT+COPS? shows operator and access technology, AT+CREG?/+CGREG?/+CEREG? show registration state in plain words.

No module handy?

There’s a clearly-marked DEMO simulated modem with canned responses - try the whole workflow without hardware, in any browser.

Everything is client-side - nothing you send or receive leaves your machine (Google Analytics for visit stats only).

This tool is free software and open source: ykasidit/web_at - issues and pull requests welcome.

Full disclosure: this post - and any code or tool it describes - was co-authored with Claude (Anthropic’s AI, via Claude Code). I directed, guided and reviewed. I don’t want to pretend otherwise.

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