zerocopy vs bytemuck

Short answerBy steady daily use, zerocopy is bigger: 3,245,504 real downloads a day against 1,311,229 for bytemuck (2.5x). 878 crates depend on zerocopy and 4,338 on bytemuck. zerocopy last shipped 11 days ago, bytemuck 3 months ago.

zerocopy

Established

Established and steady.

878 crates depend on it; small bumps on release days (1.19x the baseline).

Zerocopy makes zero-cost memory manipulation effortless. We write "unsafe" so you don't have to.

bytemuck

Widely used

Widely used and steady.

4,338 crates depend on it; no release in the last 90 days, so its count is all steady use.

A crate for mucking around with piles of bytes.

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

How they relate

Often used together: 5 tracked crates depend on both (uuid, half, hybrid-array, glam, rend). They are not always either/or.

Every number, side by side

Same window, same method	zerocopy	bytemuck
Real downloads a day	3,245,504	1,311,229
Crates that depend on it	878	4,338
Last release	0.8.63, 11 days ago	1.25.2, 3 months ago
Trend vs the field	-6%	+0%
Release-window share	18.2%	0.0%
Downloads in the window	295,559,617	121,833,300
All-time downloads	1,048,972,923	431,934,776
Versions published	174	58
License	BSD-2-Clause OR Apache-2.0 OR MIT	Zlib OR Apache-2.0 OR MIT
MSRV	1.56.0	not set
First published	Aug 15, 2018	Sep 22, 2019

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 (bytemuck, 4,338 dependents): more eyes, more answered questions, and you may already have it in your tree.
Check the release dates against your own pace: zerocopy 11 days ago, bytemuck 3 months ago.

Also in this space

num-convPulled in`num_conv` is a crate to convert between integer types without using `as` casts. This provides better...2,114,479 a day, 4 dependents ciboriumEstablishedserde implementation of CBOR using ciborium-basic775,492 a day, 902 dependents ciborium-llPulled inLow-level CBOR codec primitives775,035 a day, 10 dependents castawayPulled inSafe, zero-cost downcasting for limited compile-time specialization626,291 a day, 25 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.

Up next

Another comparison: Same method, same window. Foundational and steady vs widely used and steady.reqwest vs ureqRead it next →

Also worth your time