Kasidit’s Blog

HyperTerminal online: the long-lost Windows serial terminal, reborn in your browser

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Windows removed HyperTerminal after XP, and ever since, talking to a COM port on a modern PC has meant hunting down PuTTY or Tera Term. Back in my Windows days I kept missing a simple COM port talker that needed no installing and no learning - and even now on Ubuntu I still don’t have one, so most of the time I end up in busybox microcom. I first played with the browser’s Web Serial API in a branch of my Bluetooth GNSS app, and figured others might miss the good old simple HyperTerminal too - so here it is as a web page:

https://www.clearevo.com/hyperterminal/

Open it in Chrome or Edge on desktop, click Call, pick your COM port / USB-serial adapter (CH340, CP210x, FTDI, PL2303 and friends all work), and you get the classic experience back: the menu bar, the COM Properties dialog with bits-per-second / data bits / parity / stop bits / flow control, ASCII Setup with local echo and CR/LF options, Capture Text to a .txt file, Send Text File, and the status bar with the connect timer and 115200 8-N-1.

No install, no account, no server in the middle - it uses the browser’s Web Serial API, so the data goes straight from the page to your serial port and never leaves your machine. The UI is plain vanilla JavaScript on xp.css, which recreates the Windows XP look pixel by pixel.

No serial device handy? Try the demo ports

Under File > Properties > “Connect using” there are three clearly-marked DEMO simulated devices (not real hardware):

• a simulated AT-command modem - type AT, ATI, AT+CSQ, AT+COPS?, AT+HELP
• a simulated u-blox-like GNSS receiver (multi-constellation $GN/$GP/$GL NMEA)
• a simulated MTK-like GNSS receiver ($GP NMEA)

Both GNSS demos sit at a fixed position: McCormick Hospital in Chiang Mai, streaming valid, checksummed NMEA at 1 Hz. The demos also work in Firefox and Safari, since they don’t need Web Serial at all.

Some things the original had are not there: Zmodem/Xmodem transfers, printing, and “Wait for a Call” (a browser cannot listen for incoming serial connections). Everything else I could map onto the web platform, I did.

If you work with GNSS receivers, this pairs naturally with my Bluetooth GNSS Android app (source on GitHub) - a u-blox or NMEA device on a USB cable now needs nothing more than a browser tab to inspect.

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

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