When comparing Hack vs Iosevka, the Slant community recommends Hack for most people. In the question“What are the best programming fonts?” Hack is ranked 9th while Iosevka is ranked 18th. The most important reason people chose Hack is:
Hack is free for unlimited commercial and non-commercial use. The webfonts are hinted (TrueType instruction set) to optimize display on the screen and are built into all commonly used web font formats with each new release. They include the complete release character set and smaller (filesize) basic Latin subset releases. They are available in the [build directory](https://github.com/chrissimpkins/Hack/tree/master/build) of the repository.
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Pro Libre webfonts are available in svg, eot, ttf, woff, and woff2 formats
Hack is free for unlimited commercial and non-commercial use. The webfonts are hinted (TrueType instruction set) to optimize display on the screen and are built into all commonly used web font formats with each new release. They include the complete release character set and smaller (filesize) basic Latin subset releases. They are available in the build directory of the repository.
Pro Based on the tried and tested Bitstream Vera Sans Mono
The fonts are in the Vera Sans Mono lineage with a significant expansion of the character set (which includes Cyrillic and modern Greek character sets), new glyph shapes and modifications of the original glyph shapes, as well as improvements in metrics and hinting/TT instructions to make it more legible at small text sizes used for source code.
The changelog is available here.
Pro Powerline glyph patch is included
The regular set is patched with Powerline glyphs by default. There is no need to patch the font to use it in Powerline environments.
Pro Source code is released in UFO format
UFO source format is widely supported by all modern font editors if you would like to modify the typeface.
Pro Fixes many readability issues in Vera/DejaVu
The tilde symbol ('~'), comma (',') and semicolon (';') glyphs have been modified to be more readable at small sizes and/or on non-HD displays. In addition, the underscore symbol ('_') has been slightly lifted for alignment with surrounding characters.
Iosevka is very clear and legible on all displays and in all sizes.
Pro Several styles available
Many of the common styles are available, including Sans Serif and Slab Serif with normal, bold, italic, and bold italic styles.
Pro Support for Cyrillic and Greek letters
Iosevka is quite flexible in that it supports Cyrillic and Greek letters.
Pro Easy on user's eyes
Due to it being readable on all types of displays, Iosevka isn't hard on the user's eyes.
Pro Free and open source
Iosevka is free and open source.
Pro Large number of weights
This font comes in seven different weights, ranging from thin and extra-light to heavy.
Pro Powerline support
Includes characters for supporting Powerline/Airline for terminals and terminal editors.
Pro Ligature characters look great
Few fonts have a good ligation feature. Ligature characters (such as æ or the German ß) are supported in Iosevka and look just as you'd expect them to.
Pro Great customizability
There is full customization of styles and variants in Iosevka.
Pro IPA Support
IPA is a system containing the sounds of spoken language and includes speech qualities such as intonation.
Pro Good CJK compatibility
Iosevka integrates CJK characters well, those being characters of the Chinese, Japanese, Korean, and occasionally Vietnamese languages.
The developer is active and responds to user questions and issues.
Narrow character width uses horizontal screen space more efficiently
Pro Also variant with tiny serifs available ("Slab")
For better reading longer texts.
Con Sometimes difficult to distinguish lowercase "i" and lowercase "l"
When using a higher resolution monitor and a smaller font size, the lowercase "i" and lowercase "l" are very difficult to distinguish. The space between the dot and the remainder of the letter seems to somehow disappear, thereby making it look like a solid line, similar to the lowercase "l".
Con Fewer ligatures than other fonts
Iosevka has a nice ligation set, but it doesn't have as many ligatures as fonts like Hasklig, Monoid, or Pragmata Pro.