Welcoming Repositories Index C Ecosystem
Top Welcoming Open-Source C Repositories
Top welcoming C repositories. Scored by real 90-day external PR merge rates, maintainer review turnaround speed, and first-time contributor success.
Updated daily • Thu, 15 Oct 2026 UTC
Tracked Repos
5,292
>100 stars verified
Avg Merge Rate
75%
90-day external PRs
Open GFIs
44
Beginner friendly issues
Welcoming Tier
49
S & A Tier maintainers
Ranked C Repositories
Showing top 50 of 5,292 ranked repositories
| Rank | Repository | Tier | Score | Merge Rate | Good First Issues |
|---|---|---|---|---|---|
| #1 | Visual Pinball | S•Elite | 72.7 | 64.4% | 2 |
| #2 | The Generic Mapping Tools | S•Elite | 71.2 | 72.3% | - |
| #3 | Vulkan Loader | S•Elite | 70.8 | 87.5% | - |
| #4 | Eclipse ThreadX is an advanced real-time operating system (RTOS) designed specifically for deeply embedded applications. | S•Elite | 70.6 | 84.3% | 5 |
| #5 | Third party firmware for Asus routers (newer codebase) | S•Elite | 70.2 | 81.3% | - |
| #6 | The *cutest* framework out there for creating 2D and 3D games in C++! | A•Welcoming | 69.9 | 68.9% | - |
| #7 | openhpc/ohpc999 OpenHPC Integration, Packaging, and Test Repo | A•Welcoming | 69.9 | 70.0% | - |
| #8 | OpenPMIx Project Repository | A•Welcoming | 69.6 | 93.8% | - |
| #9 | gammu/gammu582 Gammu All Mobile Management Utilities | A•Welcoming | 69.3 | 100.0% | - |
| #10 | arendst/Tasmota24,703 Alternative firmware for ESP8266 and ESP32 based devices with easy configuration using webUI, OTA updates, automation using timers or rules, expandability and entirely local control over MQTT, HTTP, Serial or KNX. Full documentation at | A•Welcoming | 69.1 | 69.2% | - |
| #11 | DOSBox-X fork of the DOSBox project | A•Welcoming | 69.0 | 71.7% | - |
| #12 | HTML-based Rich Text solution for React Native | A•Welcoming | 69.0 | 80.0% | - |
| #13 | cilium/tetragon4,983 eBPF-based Security Observability and Runtime Enforcement | A•Welcoming | 68.9 | 60.4% | 1 |
| #14 | Flipper Zero Unleashed Firmware | A•Welcoming | 68.8 | 78.8% | - |
| #15 | zlib-ng/minizip-ng1,505 Fork of the popular zip manipulation library found in the zlib distribution. | A•Welcoming | 68.8 | 72.7% | - |
| #16 | timescale/timescaledb23,336 A time-series database for high-performance real-time analytics packaged as a Postgres extension | A•Welcoming | 68.6 | 69.0% | - |
| #17 | 🥧 An open source re-implementation of GameMaker: Studio's runner (YoYo Runner) | A•Welcoming | 68.6 | 64.6% | - |
| #18 | fwupd/fwupd4,186 A system daemon to allow session software to update firmware | A•Welcoming | 68.5 | 70.6% | 1 |
| #19 | sqliteai/warp2,483 Run the full 2.78-trillion-parameter Kimi K3 model, DeepSeek V4.1 Flash or GLM-5.3-Flash beyond available RAM by streaming activated weights directly from NVMe. A dependency-free, embeddable C inference engine. | A•Welcoming | 68.5 | 71.9% | 2 |
| #20 | A Banjo-Kazooie PC port with Anchor multiplayer, romhack and multi-language support, and a built-in randomizer. | S•Elite | 68.5 | 75.9% | - |
| #21 | pjsip/pjproject2,695 PJSIP project | A•Welcoming | 68.3 | 71.9% | - |
| #22 | Quetoo ("Q2") is a free first person shooter based on id Tech2. GPL v2 license. | S•Elite | 68.1 | 90.8% | 1 |
| #23 | Zero-code OpenTelemetry instrumentation powered by eBPF | S•Elite | 68.0 | 67.8% | 11 |
| #24 | Libtpms-based TPM emulator with socket, character device, and Linux CUSE interface. | A•Welcoming | 68.0 | 90.0% | - |
| #25 | Capstone disassembly/disassembler framework for ARM, ARM64 (ARMv8), Alpha, BPF, Ethereum VM, HPPA, LoongArch, M68K, M680X, Mips, MOS65XX, PPC, RISC-V(rv32G/rv64G), SH, Sparc, SystemZ, TMS320C64X, TriCore, Webassembly, XCore and X86. | A•Welcoming | 68.0 | 67.6% | - |
| #26 | :lock: Trezor Firmware Monorepo | A•Welcoming | 67.9 | 63.9% | 8 |
| #27 | orioledb/orioledb4,251 OrioleDB – building a modern cloud-native storage engine (... and solving some PostgreSQL wicked problems) | A•Welcoming | 67.9 | 70.7% | - |
| #28 | darktable-org/darktable12,957 darktable is an open source photography workflow application and raw developer | A•Welcoming | 67.8 | 74.5% | - |
| #29 | Protocol For Wayland run on android | A•Welcoming | 67.8 | 71.4% | - |
| #30 | Open source remake and Fan Expansion of Dungeon Keeper. | A•Welcoming | 67.8 | 68.5% | - |
| #31 | Metal Gear Solid PSX reimpl repo | A•Welcoming | 67.7 | 65.4% | - |
| #32 | RsyncProject/rsync5,146 An open source utility that provides fast incremental file transfer. It also has useful features for backup and restore operations among many other use cases. | A•Welcoming | 67.6 | 71.0% | - |
| #33 | Linux KMS/DRM based virtual Console Emulator | A•Welcoming | 67.5 | 88.0% | - |
| #34 | VisIt - Visualization and Data Analysis for Mesh-based Scientific Data | A•Welcoming | 67.5 | 75.0% | 1 |
| #35 | wolfTPM is a highly portable TPM 2.0 library, designed for embedded use. | A•Welcoming | 67.4 | 75.0% | - |
| #36 | GUI Application for FreeDV – open source digital voice for HF radio | A•Welcoming | 67.4 | 67.6% | - |
| #37 | radareorg/radare224,582 UNIX-like reverse engineering framework and command-line toolset | A•Welcoming | 67.3 | 72.7% | - |
| #38 | nanomsg/nng4,683 nanomsg-next-generation -- light-weight brokerless messaging | A•Welcoming | 67.3 | 91.7% | - |
| #39 | Multi-format archive and compression library | A•Welcoming | 67.2 | 71.5% | - |
| #40 | apache/nuttx4,064 Apache NuttX is a mature, real-time embedded operating system (RTOS) | A•Welcoming | 67.2 | 72.0% | - |
| #41 | ProFTPD source code | A•Welcoming | 67.2 | 86.8% | - |
| #42 | A GUI for the Chameleon Ultra written in Flutter for crossplatform | A•Welcoming | 67.0 | 72.2% | 1 |
| #43 | embox/embox1,599 Modular and configurable OS for embedded applications | A•Welcoming | 66.9 | 82.6% | 3 |
| #44 | mydumper/mydumper3,236 Official MyDumper Project | A•Welcoming | 66.8 | 77.8% | 5 |
| #45 | libexpat/libexpat1,390 :herb: Fast streaming XML parser written in C99 with >90% test coverage; moved from SourceForge to GitHub | A•Welcoming | 66.7 | 73.2% | 2 |
| #46 | Programs and scripts to display "inline" in Adafruit Learning System guides | A•Welcoming | 66.6 | 84.6% | 1 |
| #47 | A•Welcoming | 66.6 | 66.2% | - | |
| #48 | CFEngine Community | A•Welcoming | 66.5 | 57.0% | - |
| #49 | Universal N64 flashcart menu for wide variety of devices | A•Welcoming | 66.5 | 58.3% | - |
| #50 | FFmpeg for Jellyfin with custom extensions and enhancements | B•Solid | 66.5 | 87.5% | - |
How to Get Your C PR Merged
1
Check C-Rank™ First: Pick projects with S or A tiers to avoid maintainer ghosts and slow review cycles.
2
Run Local Verification: Ensure test suites and formatting linters pass before opening a pull request.
3
Submit in Maintainer Windows: Check the repository report card to submit when maintainers are most active.
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Frequently Asked Questions: C Open Source
What is the most welcoming C open-source repository?
The highest-ranked C repository on GetMerged is currently vpinball/vpinball, with a C-Rank score of 72.7/100 and a 64.4% PR merge rate.
How can I find good first issues in C?
You can browse verified beginner-friendly issues in C by visiting our curated Good First Issues directory at getmerged.abhishekco.de/good-first-issue/c.
What makes a C repository ‘Super Welcoming’ on GetMerged?
A ‘Super Welcoming’ (S-Tier) C repository demonstrates an external PR merge rate above 80%, a median first response time within 24 to 48 hours, active review feedback, and clear onboarding documentation.