Connect a serial device
Most USB GPS receivers talk at 9600; most modems at 115200. Nothing leaves your browser.
The evidence line records GPS time, position, accuracy and the clock difference, for pasting into the Evidence Logger.
These buttons only ask questions. They do not change modem settings.
A modem only shows the network it is connected to. It cannot prove whether a cell site is real; see the IMSI catcher guide before drawing conclusions.
Sending commands can change a device’s settings. Only send commands you understand.
Why won’t it work in my browser?
Web Serial is only in some browsers. Chrome, Edge and Opera on computers support it, and Firefox added it in version 151. Safari and Samsung Internet do not caniuse: Web Serial API support (read 23 Oct 2026). On Android, Chrome 148 added Web Serial for USB and Bluetooth serial devices Notebookcheck: Chrome 148 beta for Android adds Web Serial (Apr 2026) Chromium blink-dev: Intent to Ship Web Serial over Bluetooth on Android.
- On a computer: use Chrome or Microsoft Edge. Edge comes with Windows.
- On Android: update Chrome from the Play Store, then check chrome://version shows 148 or later.
- On iPhone or iPad: it cannot work in any browser. Use a computer.
What can a GPS receiver add?
An independent clock and position for your notes. USB GPS receivers send plain-text NMEA sentences. The tool reads the fix, position, altitude, satellites and accuracy, checks each sentence’s checksum, and compares GPS time with this computer’s clock.
Press Copy evidence line and paste it into the Evidence Logger. Indoors a receiver may take minutes to get a fix or never get one; try a window.
What can a cellular modem show?
Signal, operator, registration and, on some modems, the serving and neighbour cells. The buttons send standard read-only AT queries, plus Quectel’s cell queries. Other makers use different commands; the raw mode lets you send them if you know them.
Cell details are context, not proof. Read the IMSI catcher guide before drawing conclusions about fake base stations.
Sources
- caniuse: Web Serial API support (read 23 Oct 2026)
- Notebookcheck: Chrome 148 beta for Android adds Web Serial (Apr 2026)
- Chromium blink-dev: Intent to Ship Web Serial over Bluetooth on Android
Frequently Asked Questions
What does the Serial Device Reader do?
It connects to a device that talks over a serial port, such as a USB GPS receiver or a cellular modem, and shows what it says. For GPS it shows position, satellites, accuracy and GPS time. For modems it asks read-only questions about signal, operator and serving cell.
Why is it marked alpha?
Because it depends on the Web Serial API, which most people’s everyday browser does not have, and because serial devices vary a lot. Expect rough edges, and check anything important against the device’s own software.
Which browsers support Web Serial?
Chrome, Edge and Opera on computers, and Firefox from version 151. On Android it needs a recent Chrome; Chrome 148 added it. Safari, Samsung Internet and every browser on iPhone and iPad do not support it. The tool checks your browser and shows steps if it cannot work.
Why use GPS time for evidence?
A computer clock can be wrong by seconds or minutes. GPS time comes from satellites, so recording it alongside your own timestamps, with the difference, makes your notes easier to defend. The tool shows how far this computer’s clock is from GPS.
Can a modem detect an IMSI catcher?
Not reliably. A modem shows the cell it is connected to and nearby cells, which is useful context, but a fake base station can look normal. Our IMSI catcher guide explains what the evidence can and cannot show.
Is anything uploaded?
No. Data from the device stays in your browser. The only outside link is the optional OpenStreetMap button for a GPS position, which opens in a new tab.
Next step
Logging evidence? Paste the GPS line into the Evidence Logger. Curious about cell sites? Read the IMSI catcher guide.