Browser spectrum viewer and firmware installer for ESP32 chips, with live FFT spectra, waterfalls, tuning, gain and bandwidth controls.
With the help of LLMs, we discovered an undocumented feature in Espressif's ESP32 chips that bypasses the fixed-function modems to capture raw IQ baseband samples. ESP-WebSDR pairs with the ESP-SDR firmware to display these samples as a live spectrum and waterfall in your browser, turning supported ESP32 boards into low-cost software-defined radio receivers.
Parts of this code are AI-generated. While we put a lot of manual effort into pyespargos and the firmware for our ESPARGOS One arrays, we don't have the time to manually review all of the source code for ESP-WebSDR.
- Use a browser with Web Serial support and connect your board over USB.
- Install the matching firmware with the firmware installer.
- Open the viewer, connect to the board, and select a frequency.
The installer also includes the ESP32-S31 Ethernet / USB profile for SoapyESPSDR. Select that profile to stream continuously to desktop SDR applications. It has its own receiver control page at the board's DHCP address and does not use this serial viewer.
ESP32-C2 / ESP8684 boards are supported over UART, with up to 8,190 I/Q samples and 256–2048-bin snapshot FFTs at 80/40/16 MS/s. The packaged C2 firmware requires a 26 MHz crystal; the installer checks the crystal before writing. For CH340 bridges, use Switch to 1 Mbaud when the viewer reports transfer errors. C2 analog bandwidth covers approximately 12–20 MHz; zero selects the open capacitor setting. Controls are negotiated, so older C2 images retain their 80 MS/s-only capability and disabled bandwidth control.
Close other programs using the serial port. If automatic bootloader entry fails, hold BOOT, tap RESET, then release BOOT and reconnect in the installer.
See the ESP-SDR guide for supported chips and setup.
 Florian Euchner |
 Zoltan Doczi |
Except where otherwise noted, ESP-WebSDR is free software: you may redistribute
it and/or modify it under the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at your option)
any later version (GPL-3.0-or-later). See LICENSE for the full terms.
It is provided without any warranty, including implied warranties of
merchantability or fitness for a particular purpose.
Third-party components retain their own licenses and copyright notices.
Bundled dependency licenses are in flasher/vendor/; the font license is in
fonts.css. The accompanying ESP-SDR firmware
is licensed separately; see its license and third-party notices.
ESP32-H2 uses its Bluetooth PHY capture engine at 32, 16, approximately 10.667, and 6.4 MS/s (rate codes 7, 6, 8, and 9), with up to 16,380 complex samples and 256–2048-bin snapshot spectra. Both native USB Serial/JTAG and UART0 (TX GPIO24, RX GPIO23) are supported. The installer includes an H2 image for 2 MB or larger flash. The analog bandwidth control covers approximately 4–11 MHz; zero selects the widest filter setting. Lower rates are hardware subsampling without automatic anti-alias filtering. Continuous capture is not advertised. On a TX/RX-only adapter, enter download mode with BOOT/RESET before installation and reset afterward; the adapter cannot control the board's reset pins.