# Experimental Crystal stdlib replacements **URL:** \ **Category:** Offtopic\ **Created:** [April 9, 2026, 12:58am UTC](https://forum.crystal-lang.org/t/experimental-crystal-stdlib-replacements/8852 "2026-04-09T00:58:49Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![wontruefree](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/wontruefree/32/1467_2.png) [@wontruefree](https://forum.crystal-lang.org/u/wontruefree)\ **Post date:** [April 9, 2026, 12:58am UTC](https://forum.crystal-lang.org/t/experimental-crystal-stdlib-replacements/8852/1 "2026-04-09T00:58:49Z")
I have been experimenting with some concepts from [Casey Muratori](https://www.computerenhance.com/) and just some other thoughts on performance, dependencies, general experimentation. This has come together in this [branch](https://github.com/jkthorne/crystal/tree/pure_crystal). This fork as a few things. - [Z](https://github.com/jkthorne/z) - [YAML](https://github.com/jkthorne/yaml) - [Big Number](https://github.com/jkthorne/big_number) - [CharCov](https://github.com/jkthorne/charconv) - SIMD * * * ## Why Pure Crystal Backends? - Cross-compilation - Static linking - WASM - embedded - Docker to simplify libs - just because it is cool Honestly this is just fun and experimental. I remembered the story of [Rubinius](https://rubinius.com/) back in the day and I don’t even know if it was true but I remember one of the goals being to write parts of the stdlib in ruby and llvm. * * * ## [Z](https://github.com/jkthorne/z) The goal was to make it as compliant as possible and make it performant. Mainly because of the c library using SIMD crystal cannot get close to zlib. Which got me to start messing with SIMD in crystal. I know this [issue](https://github.com/crystal-lang/crystal/issues/3057) exists but I am just playing around with it. | | Z (pure Crystal) | stdlib/libz | Ratio | | --- | --- | --- | --- | | Compress — Deflate (text) | 140 MB/s | 483 MB/s | 0.3x | | Compress — Gzip (text) | 135 MB/s | 461 MB/s | 0.3x | | Compress — Deflate (random) | 26 MB/s | 58 MB/s | 0.5x | | Decompress — Deflate (text) | 2,910 MB/s | 4,749 MB/s | 0.6x | | Decompress — Gzip (text) | 766 MB/s | 4,547 MB/s | 0.2x | * * * ## [CharConv](https://github.com/jkthorne/charconv) : [Forum Post](https://forum.crystal-lang.org/t/charconv-pure-crystal-iconv-replacement/8776) Replaces libiconv with support for 150+ encodings: all ISO-8859-_, CP_, KOI8-\* single-byte encodings, UTF-7/16/32, full CJK (Shift\_JIS, EUC-JP, GB2312, GBK, GB18030, Big5, EUC-KR, EUC-TW), and stateful codecs (ISO-2022-JP/CN/KR, HZ-GB-2312). Supports //IGNORE and //TRANSLIT modes. | Conversion | charconv | system iconv | Ratio | | --- | --- | --- | --- | | ASCII → ASCII | 73 µs | 11.89 ms | 162x | | UTF-8 → ISO-8859-1 | 3.43 ms | 14.62 ms | 4.3x | | ISO-8859-1 → UTF-8 | 2.08 ms | 14.24 ms | 6.9x | | UTF-8 → UTF-8 (mixed widths) | 4.92 ms | 11.98 ms | 2.4x | | CP1252 → UTF-8 | 2.50 ms | 17.24 ms | 6.9x | | UTF-16BE → UTF-8 | 3.73 ms | 10.83 ms | 2.9x | | UTF-8 → UTF-16LE | 4.57 ms | 10.11 ms | 2.2x | * * * [BigNumber](https://github.com/jkthorne/big_number) : [Forum Post](https://forum.crystal-lang.org/t/big-number-pure-crystal-gmp-replacement/8775/18) | Operation | 1 limb (19 dig) | 10 limbs (190 dig) | 50 limbs (950 dig) | 100 limbs (1.9k dig) | 1000 limbs (19k dig) | | --- | --- | --- | --- | --- | --- | | add | 0.77x | 0.98x | 1.12x | 1.09x | 1.18x | | mul | 0.77x | 1.35x | 2.62x | 2.62x | 3.21x | | div | 0.98x | 2.54x | 2.36x | 2.62x | | | to\_s | 1.95x | 3.36x | 5.16x | 5.37x | 4.58x | * * * ## [YAML](https://github.com/jkthorne/yaml) | Fixture | Size | libyaml | pure Crystal | Ratio | | --- | --- | --- | --- | --- | | trivial | 11 B | 333k ips | 429k ips | 1.29x faster | | flat\_mapping | 1.7 KB | 12.0k ips | 12.4k ips | 1.03x faster | | flow\_collections | 4.8 KB | 4.7k ips | 5.2k ips | 1.12x faster | | nested | 32 KB | 1.02k ips | 989 ips | 0.97x | | block\_scalars | 1.6 KB | 28.9k ips | 24.5k ips | 0.85x | | strings\_heavy | 6.9 KB | 8.9k ips | 5.2k ips | 0.59x | | large\_config | 49 KB | 727 ips | 656 ips | 0.90x | * * * ## SIMD Vectors (SIMDVector(T, N)) - SIMDVectorType and SIMDVectorInstanceType - LLVM vector instruction bindings - Codegen: simd\_splat, simd\_extract, simd\_insert, simd\_binary, simd\_compare * * * ## Finally I am curious if people would use this, be interested in this, general feedback. I have some ideas for my own web framework and will probably see if I can include any of this in some of the ideas I have. Thanks for reading this far! ---
**Author:** ![wontruefree](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/wontruefree/32/1467_2.png) [@wontruefree](https://forum.crystal-lang.org/u/wontruefree)\ **Post date:** [April 9, 2026, 2:14am UTC](https://forum.crystal-lang.org/t/experimental-crystal-stdlib-replacements/8852/2 "2026-04-09T02:14:07Z")
This is a small Z update with some SIMD updates | Benchmark | libz (C) | Crystal+SIMD | Ratio | | --- | --- | --- | --- | | Gzip compress (compressible 990KB) | 1.84ms | 4.77ms | 2.6x slower | | Gzip compress (random 1MB) | 17.67ms | 33.42ms | 1.9x slower | | Gzip compress (repetitive 1MB) | 1.86ms | 4.73ms | 2.5x slower | | Zlib compress (compressible 990KB) | 1.88ms | 3.99ms | 2.1x slower | | Zlib compress (random 1MB) | 16.98ms | 31.18ms | 1.8x slower | ---
**Author:** ![weirdbricks](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/weirdbricks/32/1741_2.png) [@weirdbricks](https://forum.crystal-lang.org/u/weirdbricks)\ **Post date:** [April 19, 2026, 3:23am UTC](https://forum.crystal-lang.org/t/experimental-crystal-stdlib-replacements/8852/3 "2026-04-19T03:23:24Z")
In my opinion, Crystal’s ability to compile to a single binary is one of it’s greatest strengths, so I’m excited about enabling this with pure Crystal implementations. Thank you for this @wontruefree !