Crates / Compare / serde_json vs rmp-serde
Rust crates side by side · data Oct 24, 2026
serde_json vs rmp-serde
Short answerBy steady daily use, serde_json is bigger: 4,294,696 real downloads a day against 345,933 for rmp-serde (12.4x). 113,141 crates depend on serde_json and 1,717 on rmp-serde. serde_json last shipped 13 days ago, rmp-serde 10 months ago.
serde_json
FoundationalFoundational and steady.
113,141 crates depend on it; downloads don't spike on releases.
A JSON serialization file format
rmp-serde
Widely usedWidely used and steady.
1,717 crates depend on it; no release in the last 90 days, so its count is all steady use.
Serde support for MessagePack
serde_jsonrmp-serde · 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 | serde_json | rmp-serde |
|---|---|---|
| Real downloads a day | 4,294,696 | 345,933 |
| Crates that depend on it | 113,141 | 1,717 |
| Last release | 1.0.154, 13 days ago | 1.3.1, 10 months ago |
| Trend vs the field | -6% | -4% |
| Release-window share | 3.4% | 0.0% |
| Downloads in the window | 381,172,075 | 29,462,141 |
| All-time downloads | 1,484,483,384 | 144,279,307 |
| Versions published | 186 | 43 |
| License | MIT OR Apache-2.0 | MIT |
| MSRV | 1.71 | 1.85 |
| First published | Aug 7, 2015 | Aug 24, 2015 |
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 (serde_json, 113,141 dependents): more eyes, more answered questions, and you may already have it in your tree.
- Check the release dates against your own pace: serde_json 13 days ago, rmp-serde 10 months ago.
Also in this space
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
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