HxD is described as 'Carefully designed and fast hex editor which, additionally to raw disk editing and modifying of main memory (RAM), handles files of any size' and is a very popular Hex Editor in the development category. There are more than 50 alternatives to HxD for a variety of platforms, including Windows, Linux, Mac, BSD and Android apps. The best HxD alternative is ImHex, which is both free and Open Source. Other great apps like HxD are wxHexEditor, 010 Editor, wxMEdit and Hex Fiend.
BinEd is a hex editor tool, which allows to directly browse and edit content of any file or binary data.
Hiew (short for Hackers view) is a popular console hex editor for DOS and Windows written by Eugene Suslikov (sen). Amongst its feature set is its ability to view files in text, hex and disassembly mode.
Malcat is a feature-rich hexadecimal editor / disassembler / decompiler for reverse engineers and malware analysts. It has support for many file formats and CPUs, can scan for signatures, decrypt/decompress data, diff files and run python scripts.
A hexadecimal low level disk editor with extensive templates for NTFS, FAT and exFAT partitions
You got a binary file and don't know its contents. Or some software creates binary files where you have a specification but don't want to decode them manually.
The Hex Editor From Hell! Hecate is a terminal hex editor that, instead of putting the (ASCII) representation of bytes way out on the right side of the screen, it puts the interpreted values directly beneath the hex representation.
HexEd.it is a free hex editor for all modern operating systems. It uses web technology to enable online hexediting, directly in the browser. Analyse binary dumps and files, read, manipulate, write, import and export any data in this webapp.
HexEdit is a hexadecimal file editor for Microsoft Windows. HexEdit allows the user to view and edit any type of file, no matter what format it is saved in.
As the name implies, this is a hex editor. It aims to be a good general-purpose hex editor and to have a wide selection of features for analysing and annotating binary file formats.
XVI32 is a freeware hex editor. XVI32 has the following main features.
Open Source powerful and flexible Hex-Editor, with multiple colour-schemes that allow easy visual indication of byte-magnitude.
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It can edit/search only in ASCII, no hex. It has search, but no replace tool. It's enough for editing a few bytes, but only in ASCII, no binary/hex, and definitely not for heavy duty of any kind. It does open large files, but what use is that, as it cannot search/replace anything (and when/if it does, it must be in ASCII).