head to head · open source
monolog vs defmt
monolog has 21,405 GitHub stars, 1,910 forks, 3 open issues and last shipped yesterday. defmt has 1,229 stars, 132 forks, 117 open issues and last shipped 12 days ago. monolog leads on adoption by 1,642% (21,405 vs 1,229 stars). monolog is written in PHP under MIT; defmt is written in Rust under Apache-2.0. monolog has attracted 9% as many forks as stars, defmt 11%. monolog was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (logging), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| monolog | defmt | |
|---|---|---|
| GitHub stars | ★ 21K | ★ 1.2K |
| License | MIT | Apache-2.0 |
| Written in | PHP | Rust |
| Last push | 2026-09-19 | 2026-09-08 |
| Forks | ⑂ 1.9K | ⑂ 132 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick monolog if
- You weight community size — 21K stars and counting
- You want the MIT license terms
- Your stack matches PHP
- You value the larger contributor base for long-term maintenance
pick defmt if
- You want the defmt feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Rust
- You evaluated both and defmt fits your workflow better
About monolog
Monolog is a logging library for PHP that sends log records to files, sockets, inboxes, databases, and various web services. It ships with the handlers, formatters, and processors needed to route records where they belong, and special handlers allow more advanced logging strategies than a single output stream. The library lives in the PHP ecosystem and is distributed through Packagist as monolog/monolog . It is released under the MIT license and has been developed for sixteen years, with more than twenty one thousand stars and roughly nineteen hundred forks on GitHub.
read the full monolog overview →
About defmt
defmt is an efficient, deferred formatting logging framework for embedded systems written in Rust, aimed at firmware developers building for resource constrained devices such as microcontrollers.
read the full defmt overview →
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Frequently asked questions
Is monolog or defmt more popular?
monolog has 21,405 GitHub stars and defmt has 1,229. monolog has the larger community by that measure.
Are monolog and defmt free?
Both are open source. monolog is licensed under MIT and defmt under Apache-2.0. Neither carries a licence fee.
What is the difference between monolog and defmt?
monolog is written in PHP and defmt in Rust. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, monolog or defmt?
Choose monolog if you want the larger community (21,405 stars) or its MIT licence terms. Choose defmt if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.