crc32fast vs crc32c

Short answerBy steady daily use, crc32fast is bigger: 2,229,287 real downloads a day against 209,580 for crc32c (10.6x). 1,440 crates depend on crc32fast and 345 on crc32c. crc32fast last shipped 4 days ago, crc32c 2.4 years ago.

crc32fast

Widely used

Widely used and steady.

1,440 crates depend on it; downloads don't spike on releases.

Fast, SIMD-accelerated CRC32 (IEEE) checksum computation

crc32c

Established

Established and gaining.

345 crates depend on it; no release in the last 90 days, so its count is all steady use.

Safe implementation for hardware accelerated CRC32C instructions with software fallback

crc32fastcrc32c · 100% = that crate's normal quiet day, so a spike to 300% is triple its usual traffic

Every number, side by side

Same window, same method	crc32fast	crc32c
Real downloads a day	2,229,287	209,580
Crates that depend on it	1,440	345
Last release	1.5.3, 4 days ago	0.6.8, 2.4 years ago
Trend vs the field	+6%	+17%
Release-window share	6.6%	0.0%
Downloads in the window	203,725,325	20,165,366
All-time downloads	791,416,317	92,671,537
Versions published	21	16
License	MIT OR Apache-2.0	Apache-2.0/MIT
MSRV	1.63	not set
First published	Nov 13, 2018	Sep 15, 2017

Which to pick

Downloads tell you what is common, not what fits. Each crate's own description above says what it is for; when the jobs differ, pick by the job.
When both fit, prefer the one more crates depend on (crc32fast, 1,440 dependents): more eyes, more answered questions, and you may already have it in your tree.
Check the release dates against your own pace: crc32fast 4 days ago, crc32c 2.4 years ago.

Also in this space

crcEstablishedRust implementation of CRC with support of various standards930,857 a day, 601 dependents foldhashEstablishedA fast, non-cryptographic, minimally DoS-resistant hashing algorithm3,043,165 a day, 333 dependents fastrandWidely usedA simple and fast random number generator2,895,139 a day, 1,809 dependents adler2Pulled inA simple clean-room implementation of the Adler-32 checksum1,994,630 a day, 18 dependents

Compare 4 of them side by side →

Method

Real downloads = the median day with no release that day or the day before, from the crates.io API (Jul 27, 2026 to Oct 23, 2026). Raw crates.io counts include CI and bots and run high (why); the method is from our 90-day study.

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