Awesome

Hex Fiend

A fast and clever open source hex editor for macOS.

Download the latest version from the releases page.

Insert, delete, rearrange. Hex Fiend does not limit you to in-place changes like some hex editors.
Work with huge files. Hex Fiend can handle as big a file as you’re able to create. It’s been tested on files as large as 118 GB.
Small footprint. Hex Fiend does not keep your files in memory. You won’t dread launching or working with Hex Fiend even on low-RAM machines.
Fast. Open a huge file, scroll around, copy and paste, all instantly. Find what you’re looking for with fast searching.
Binary diff. Hex Fiend can show the differences between files, taking into account insertions or deletions. Simply open two files in Hex Fiend and then use the File > Compare menus.
Smart saving. Hex Fiend knows not to waste time overwriting the parts of your files that haven’t changed, and never needs temporary disk space.
Data inspector. Interpret data as integer or floating point, signed or unsigned, big or little endian.
Binary templates. Visualize the structure of a file through scripting. See documentation.
Embeddable! It’s really easy to incorporate Hex Fiend’s hex or data views into your app using the Hex Fiend framework. Its permissive BSD-style license won’t burden you. See the API reference for details. Check out the projects using Hex Fiend.