There are different types of editors used to change the context of the given file. Most of the computer users aware of text editors. But there are other less-known editors used by different professions. Hex editors are mainly used by reverse engineers, system administrators, application developers, etc.
What is Hex or Hexadecimal Editor?
Hex editors used to edit files where these files are generally structured in a hexadecimal format. The logic is the same as text files where they are structured in ASCII/text format. Hexadecimal numbering system like decimal where we use in our daily life.
Free Hex Editor (frehed)
Free Hex Editor is provided by HHD software. It is especially good in editing large files in hexadecimal mode. It is distributed in the freemium model and provides basic features for free. It allows you to find data patterns in multi-gigabyte files in seconds. Supports expression rich regular expressions. Easily create file patches just one click. The flexible user interface can easily be configured for your convenience. Supports multiple cores to make it exceedingly faster. Can be downloaded from the following link.
http://www.hhdsoftware.com/Download/free-hex-editor-neo.exe

HxD
HxD is developed by Mh-Nexus. HxD is a popular hex editor between reverse engineers. It has a rich feature set. It provides install-able and portable editions. It has the ability to edit RAM or main memory contents but as you expect it requires Administrator privileges. It can editor disk drives like hard disks, floppy disks, zip-disks, cd, etc. HxD has a flexible and fast search engine. Edited content can be exported in several data formats like Pascal, C, Java, C# source, Plain text, Hex files, etc. HxD can provide basic data analytics or statistics about the hex file. HxD can be downloaded from the following link.
ftp://wa651f5:anonymous@mh-nexus.de/HxDSetupEN.zip

UltraEdit
UltraEdit has a rich feature set like previous examples. It has also a shiny and modern look. UltraEdit support themes that will give different look to the hex editor. It supports multi-caret or multi-select where we can add the same characters into multiple places single type. Like other hex editors fast search. It supports integrated FTP, Ssh, Telnet connections, and remote files. It supports Windows, Mac, and Linux operating systems. UltraEdit can be downloaded from the following link.
https://downloads.ultraedit.com/main/ue/win/ue_english_64.exe

ZTreeWin
ZTreeWin is a command-line or MS-DOS-based hex editor. It has fewer features than other hex editor but has the ability to work from the command line or MS-DOS. It supports Unicode applications. Enhanced color configuration. Extended status information about system and login. The history list for marked entries which has no limit.

PSPad
PSPad is a freeware text and code editor. It can edit multiple files at the same time. Ability to save current work in order to open later. Ftp client to edit remote files directly. Macro recorder which can record, save, and run macros. diff functionality with coloring. Syntax highlighting according to file type. RTF, HTML, TeX export capability. It has an installer and portable versions. PSPad can be downloaded from the following link.
http://www.fosshub.com/PSPad.html

Notepad++ Hexeditor Plugin
Notepad++ is actually a text editor but it has plugin that provides additional features. Hex editor plugin is one of them. Hex editor can be installed from Plugin
-> Plugin Manager
-> Show Plugin Manager
-> Available
.Notepadd++ provides simple features as Hex editor. We can view change the content of the current file.

HexEd.it (Web Based)
With the advancement of the web and internet most of the services, applications are provided web-based. HexEd.it
is a web-based hex editor which provides very clean and simple GUI via the web browser. As you expect there is no need to install software to exit hex files. Just navigate to the https://hexed.it URL. As a web-based hex editor, it provides useful features about the display, date format, hex area settings, data type visibility, Address and text search, etc. As you expect in order to display and edit a file as hex you need to upload it with the Open file button. There is no fee about usage but you make a donation to this app or project via bitcoin or PayPal.

Thanks a lot.
I do lots of memory dump level debugging, and I’ve had problems with HxD due to the lack of endianness support and slow and lackluster export features.
Thanks to you, I installed Free Hex Editor Neo, and found out that it is simply the best for this kind of jobs: endianness support and powerful export features. Just perfect. The latter features are for the non-free version only though.
Again, thanks a lot.
Hello. And Bye.