I built three small tools that run entirely in the browser — no backend, no signup, nothing uploaded:
JSON Grid (https://jsongrid.trendx.uk) — paste/drop JSON, view it as a navigable grid table, pretty-print, validate, diff two values, search. It also converts Salesforce Apex debug output into JSON.
Apex Flow (https://apexflow.trendx.uk) — open a local Salesforce/LWC/Java project folder (File System Access API) and it builds class diagrams + recursive call-flow charts with Mermaid.
SF Debug Viewer (https://apexdebug.trendx.uk) — paste a raw Apex debug log and get a collapsible call tree with SOQL/DML breakdown, exceptions, and method timings.