Tab to Guitar Pro - what this site is built with

alphaTab 1.8.4 (writes the Guitar Pro file)
  https://github.com/CoderLine/alphaTab - Mozilla Public License 2.0, see alphatab-MPL-2.0.txt
  Served unchanged as /assets/alphaTab-1.8.4.min.js

PDF.js 3.11.174 (opens PDF files)
  https://github.com/mozilla/pdf.js - Apache License 2.0, see pdfjs-Apache-2.0.txt
  Served unchanged as /assets/pdf-3.11.174.min.js and /assets/pdf.worker-3.11.174.min.js

Fonts, each under the SIL Open Font License 1.1:
  Bricolage Grotesque - see bricolage-grotesque-OFL.txt
  Instrument Sans - see instrument-sans-OFL.txt
  JetBrains Mono - see jetbrains-mono-OFL.txt

The picture reader recognises digits and letters by comparing them with small 14x18 grids.
Those grids were drawn once from the fonts Liberation, DejaVu, Roboto, Gelasio, Edwin, Leland and Bravura.