WebModbus guide
WebModbus (also searched as "web Modbus" or "웹 모드버스") is a free web tool that connects to Modbus devices straight from the browser to read and write registers and coils. Use it to check or monitor PLCs, drives, and sensors that speak Modbus RTU, ASCII, or TCP, without installing a desktop program.
Features
- Serial RTU/ASCII: connect to USB-RS485/RS232 adapters with Web Serial in Chrome or Edge.
- TCP and UDP: reach Modbus TCP, TCP Security (TLS), UDP, and RTU/ASCII over TCP/UDP through a local bridge that runs on your own computer.
- Multiple request windows: each window has its own Slave ID, function code, start address, quantity, and poll interval, and they poll side by side. You can prepare windows and definitions before connecting.
- Data formats: view 16/32/64-bit integers, floats, byte and word order, and DEC/HEX addresses cell by cell.
- Function dialogs and test center: send 05, 06, 08, 11, 15, 16, 17, 22, 23, and 43/14, or type raw frames with the CRC/LRC added for you. Address scan and slave scan are included.
- Real-time sharing: let others see your request windows and values through one link, with limits on guests and permissions. Every remote write needs the host's confirmation.
- Google account sync: window layout and settings follow you across devices signed in to the same account.
- Themes and languages: 14 themes including dark ones, and Korean, English, Japanese, Chinese, Vietnamese, Spanish, German, French, and Russian.
Getting started
- Open WebModbus. Serial connections need desktop Chrome or Edge on an HTTPS address.
- In the connection settings choose serial or TCP/UDP, set the port and baud rate (or host and port), and connect.
- Create a request window with "New request", then press F8 to set the Slave ID, function code (for example 03 Holding Registers), start address, and quantity.
- Read once or start polling, and change the data format from the Display menu. Writes ask for one more confirmation before they are sent.
- Use the Display menu for colors, font, scaling, value names, error counters, and the real-time chart (Alt+R), as in Modbus Poll.
FAQ
Is it free? Do I need an account?
It is free and works without an account. Google sign-in is only needed for syncing between devices.
Are my device values sent to a server?
No. Communication with the device happens in your browser (or the bridge on your own computer), and the values you read are not stored on a server. If you turn sharing on, they go only to the guests you approve. See the privacy policy.
Does it work in Firefox or Safari?
The interface opens, but serial connections need Chrome or Edge because other browsers lack Web Serial. TCP/UDP works in other browsers when the local bridge is running.
Is it the same as Modbus Poll?
The workflow is similar, but WebModbus is an independent project with no affiliation to Modbus Poll (Witte Software) or the Modbus Organization. "Modbus" is a registered trademark of Schneider Electric USA, Inc.