Free Online Serial Monitor & USB Serial Capture Tool
Connect to Arduino, ESP32, and USB serial devices, view live output, and download a raw text log without installing another application.
Connection
Choose the baud rate your firmware uses, then connect to a serial device from a Chromium-based desktop browser.
Serial Data Text Box
0 characters captured
Need repeatable serial logging?
DaqSense adds saved profiles, parser rules, live tables, formulas, raw-plus-parsed recording, and CSV or Excel exports for repeatable hardware tests.
How to Use This Online Serial Monitor
- Connect your Arduino, ESP32, STM32, Raspberry Pi Pico, or USB-to-UART adapter to your computer.
- Close Arduino Serial Monitor, PlatformIO Device Monitor, PuTTY, or any other program that may already have the port open.
- Select the baud rate used by your firmware, click Connect, and choose the device in the browser prompt.
- Watch the incoming text, then copy it or download the current capture as a timestamped
.txtfile.
The tool uses the browser's Web Serial API to request access to a serial device, open the selected port, and append incoming bytes to the text box. It is designed for quick connection checks, Arduino and ESP32 debug logs, boot messages, and short sensor captures. Click Load Sample if you want to try the copy and download workflow without connecting hardware.
Privacy, Browser Support, and Device Access
The serial connection and captured text stay in your browser; the page does not send your serial data to DaqSense servers. Your browser asks you to choose a port before opening it, and you can disconnect at any time. Web Serial requires a secure page and a compatible desktop browser. If the Connect button is unavailable, open this page in a current version of Chrome, Edge, or another desktop browser that exposes the Web Serial API.
| Requirement | What to check |
|---|---|
| Browser | Use a desktop browser with Web Serial support. Chrome and Edge are the safest choices. |
| Connection | Use HTTPS and connect the board with a data-capable USB cable. |
| Port access | Close other serial monitors because most serial ports can be opened by only one program at a time. |
| Driver | Boards using CH340, CP210x, or FTDI adapters may require an operating-system driver. |
Common Baud Rates for Arduino and ESP32
Arduino sketches often print serial data at 9600 or 115200 baud. ESP32 projects commonly use 115200 baud for application logs, and 74880 baud can be useful for some boot messages. The selected baud rate must match the value used by your firmware, such as Serial.begin(115200).
Serial Port Troubleshooting
| Problem | Likely fix |
|---|---|
| The device is not listed | Reconnect the USB cable, confirm the OS detects the board, and check the required driver. |
| Access denied or port busy | Close Arduino Serial Monitor, PlatformIO, PuTTY, Python loggers, and other programs using the port. |
| Unreadable or garbled output | Match this page's baud rate to the value passed to Serial.begin(...). |
| Output stops after disconnecting | Reconnect and choose the port again; refreshing the page ends the browser session. |
For a complete checklist, see how to fix an Arduino or USB serial port that is not showing. If the connection works but the text is unreadable, use the ESP32 serial garbage and baud-rate checklist.
Capture Limits and File Format
This page keeps up to one million characters in the visible text box. During a longer capture, the oldest displayed text is removed after that limit is reached. The Download button saves the text currently shown as a raw .txt file; it does not parse columns, add durable timestamps, or create a managed recording session. For clean spreadsheet data, read how to save Arduino serial data to CSV.
Online Serial Monitor vs. Serial Data Logger
| Free browser tool | DaqSense desktop |
|---|---|
| Quick incoming-text check | Repeatable recording sessions |
| Raw text download | Raw and parsed CSV or Excel output |
| One-time baud selection | Saved device and parser profiles |
| No transformations | Live tables, formulas, and calibration columns |
Frequently Asked Questions
Do I need to install a serial monitor?
No. A compatible desktop browser can connect directly to a serial device from this secure page. Your operating system may still need the correct USB-to-serial driver for the board or adapter.
Does DaqSense upload my captured serial data?
No. The connection and text capture run locally in the browser. The page does not send the captured stream to DaqSense servers.
Can this tool save serial data to CSV?
This page downloads the visible raw stream as a text file. Use a dedicated logger when you need parsed columns, timestamps, formulas, repeatable profiles, or CSV and Excel exports.
Why does my serial output look like random characters?
The most common cause is a baud-rate mismatch. Select the same rate used by your firmware, such as 9600 or 115200.
Related Serial Logging Guides
- Save Arduino serial data to CSV
- Parse serial rows into engineering units
- Compare Arduino Serial Monitor alternatives
- Troubleshoot a missing Arduino serial port
Need structured logging instead of a quick text capture? DaqSense is built for repeatable serial test workflows with parser rules, profiles, formulas, raw capture, and CSV exports.