Welcoming Repositories Index Haskell Ecosystem
Top Welcoming Open-Source Haskell Repositories
Top welcoming Haskell repositories. Scored by real 90-day external PR merge rates, maintainer review turnaround speed, and first-time contributor success.
Updated daily • Sun, 30 Aug 2026 UTC
Tracked Repos
1,024
>100 stars verified
Avg Merge Rate
88%
90-day external PRs
Open GFIs
43
Beginner friendly issues
Welcoming Tier
37
S & A Tier maintainers
Ranked Haskell Repositories
Showing top 50 of 1,024 ranked repositories
| Rank | Repository | Tier | Score | Merge Rate | Good First Issues |
|---|---|---|---|---|---|
| #1 | NixOS/nixfmt1,591 The official formatter for Nix code | S•Elite | 76.9 | 91.1% | - |
| #2 | Pipe your nix-build output through the nix-output-monitor a.k.a nom to get additional information while building. | S•Elite | 73.4 | 86.7% | - |
| #3 | A package index for the Haskell ecosystem | S•Elite | 72.0 | 91.5% | 3 |
| #4 | The Daml smart contract language | S•Elite | 71.4 | 86.9% | 2 |
| #5 | The Software Analysis Workbench | S•Elite | 71.2 | 88.6% | 7 |
| #6 | Typed eDSL for writing UPLC /ˈpluː.tɑːk/ | S•Elite | 71.1 | 95.5% | 1 |
| #7 | Addresses and mnemonic manipulation & derivations | B•Solid | 70.7 | 96.6% | - |
| #8 | Optics as an abstract interface | S•Elite | 70.6 | 100.0% | - |
| #9 | hadolint/hadolint12,366 Dockerfile linter, validate inline bash, written in Haskell | S•Elite | 70.6 | 92.9% | 1 |
| #10 | A toolkit for enforcing logical specifications on neural networks | A•Welcoming | 69.9 | 86.8% | - |
| #11 | Actor-based, safely typed, fast programming language. | A•Welcoming | 69.7 | 82.2% | - |
| #12 | experimental solidity compiler | A•Welcoming | 67.8 | 85.1% | - |
| #13 | This rule is for uBlacklist. there is also a rule for uBlock Origin in Firefox for Android. | B•Solid | 67.4 | 100.0% | - |
| #14 | ⏩ NeoHaskell is a dialect of Haskell that is focused on newcomer-friendliness and productivity. | A•Welcoming | 67.1 | 83.5% | 2 |
| #15 | Generate all the things (focusing on research software) | A•Welcoming | 66.5 | 89.3% | - |
| #16 | Servant is a Haskell DSL for describing, serving, querying, mocking, documenting web applications and more! | A•Welcoming | 65.6 | 86.2% | - |
| #17 | A modern step-through debugger for GHC Haskell | A•Welcoming | 65.5 | 86.3% | 6 |
| #18 | reflex-frp/reflex1,115 Interactive programs without callbacks or side-effects. Functional Reactive Programming (FRP) uses composable events and time-varying values to describe interactive systems as pure functions. Just like other pure functional code, functional reactive code is easier to get right on the first try, maintain, and reuse. | A•Welcoming | 65.5 | 87.5% | - |
| #19 | A Direct-to-Driver open mobility platform powering the next-generation of mobility applications in India. | A•Welcoming | 65.4 | 78.6% | - |
| #20 | Symbolic formula representation and solver interaction library | A•Welcoming | 65.2 | 91.7% | - |
| #21 | dmjio/miso2,427 :ramen: A tasty Haskell web framework | A•Welcoming | 65.1 | 79.8% | - |
| #22 | sol/hpack665 hpack: A modern format for Haskell packages | A•Welcoming | 65.0 | 100.0% | - |
| #23 | Haskell-based shell scripting language | B•Solid | 64.9 | 100.0% | - |
| #24 | GaloisInc/cryptol1,217 Cryptol: The Language of Cryptography | A•Welcoming | 64.9 | 87.0% | - |
| #25 | Publishes curated news about the Haskell programming language. | B•Solid | 64.5 | 100.0% | - |
| #26 | nmattia/niv1,856 Easy dependency management for Nix projects | B•Solid | 64.4 | 88.5% | - |
| #27 | A type-safe Haskell SQL library | A•Welcoming | 64.4 | 87.1% | 3 |
| #28 | Automatically generate Haskell bindings from C header files | A•Welcoming | 64.2 | 92.5% | - |
| #29 | HTTP server & command-line for managing UTxOs and HD wallets in Cardano. | A•Welcoming | 64.1 | 86.5% | - |
| #30 | Set up a GHC API session for various Haskell Projects | A•Welcoming | 64.1 | 92.3% | - |
| #31 | rzk-lang/rzk292 An experimental proof assistant based on a type theory for synthetic ∞-categories. | A•Welcoming | 64.0 | 91.9% | - |
| #32 | nasa/ogma574 Generator of runtime monitors for flight and robotics applications. | B•Solid | 63.7 | 95.4% | - |
| #33 | Implementation of the Hydra Head protocol | A•Welcoming | 63.4 | 74.5% | 15 |
| #34 | Haskell implemented with combinators | B•Solid | 63.0 | 69.6% | - |
| #35 | Windows-native Nix evaluator - Haskell for logic, C99 for data. Parser, lazy evaluator, content-addressed store, builder, binary substituter. | B•Solid | 62.7 | 85.4% | - |
| #36 | ClickHouse Native protocol driver in Haskell | B•Solid | 62.7 | 100.0% | - |
| #37 | agda/agda2,919 Agda is a dependently typed programming language / interactive theorem prover. | A•Welcoming | 62.7 | 78.3% | - |
| #38 | wireapp/wire-server2,782 🇪🇺 Wire back-end services | A•Welcoming | 62.6 | 73.2% | - |
| #39 | IntersectMBO/plutus1,634 The Plutus language implementation and tools | A•Welcoming | 62.4 | 78.3% | 1 |
| #40 | Liquid Types For Haskell | A•Welcoming | 62.3 | 83.5% | - |
| #41 | vekatze/neut1,008 A functional programming language with static memory management | B•Solid | 61.7 | 100.0% | - |
| #42 | Espial is an open-source, web-based bookmarking server. | B•Solid | 61.5 | 100.0% | - |
| #43 | Contributed modules for xmonad | A•Welcoming | 61.5 | 84.6% | 1 |
| #44 | Build terminal applications using functional reactive programming (FRP) with Reflex FRP. | B•Solid | 61.4 | 96.4% | - |
| #45 | Crucible is a library for symbolic simulation of imperative programs | A•Welcoming | 61.1 | 86.1% | - |
| #46 | A fourk of ormolu that uses four space indentation and allows arbitrary configuration. Don't like it? PRs welcome! | A•Welcoming | 61.0 | 78.9% | - |
| #47 | Code used throughout the Cardano eco-system | A•Welcoming | 60.8 | 79.2% | 1 |
| #48 | Pure haskell mysql driver | A•Welcoming | 60.8 | 75.0% | - |
| #49 | Hackage-Server: A Haskell Package Repository | A•Welcoming | 60.8 | 74.1% | - |
| #50 | Syntax highlighting support for Haskell in Visual Studio Code | B•Solid | 60.7 | 100.0% | - |
How to Get Your Haskell 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: Haskell Open Source
What is the most welcoming Haskell open-source repository?
The highest-ranked Haskell repository on GetMerged is currently NixOS/nixfmt, with a C-Rank score of 76.9/100 and a 91.1% PR merge rate.
How can I find good first issues in Haskell?
You can browse verified beginner-friendly issues in Haskell by visiting our curated Good First Issues directory at getmerged.abhishekco.de/good-first-issue/haskell.
What makes a Haskell repository ‘Super Welcoming’ on GetMerged?
A ‘Super Welcoming’ (S-Tier) Haskell 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.