Free tools that run in your browser

Each tool does one job, needs no account, and processes your files on your own device — nothing is uploaded.

Replace or add an EPUB cover image and fix the title and author. Works offline in your browser.

Call center staffing: agents for a service level, ASA, occupancy and shrinkage. Erlang B included.

Color difference between two colors: ΔE 2000, CIE76, CIE94 and CMC from HEX, RGB or Lab.

Encrypt files into a password-protected ZIP (AES-256 or Windows-compatible) without uploading them.

Set a JPG or PNG to 300 DPI (or any value) without resizing or quality loss, and see the print size.

Convert vCard contacts to CSV (Excel, Google) and back, merge or split VCF files — privately.

Create a .ics calendar invite with time zone, reminder and repeat, plus Google and Outlook links.

See distance, elevation gain and profile of a GPX track; convert to KML, GeoJSON or CSV.