Welcoming Repositories Index Scala Ecosystem
Top Welcoming Open-Source Scala Repositories
Top welcoming Scala 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
1,174
>100 stars verified
Avg Merge Rate
90%
90-day external PRs
Open GFIs
9
Beginner friendly issues
Welcoming Tier
29
S & A Tier maintainers
Ranked Scala Repositories
Showing top 50 of 1,174 ranked repositories
| Rank | Repository | Tier | Score | Merge Rate | Good First Issues |
|---|---|---|---|---|---|
| #1 | yaes-io/yaes139 A direct-style effect system in Scala 3 that tracks effects using context parameters | B•Solid | 76.3 | 100.0% | - |
| #2 | The Scala version of MyBatis SQL Mapper | B•Solid | 75.9 | 100.0% | - |
| #3 | wvlet/wvlet157 A flow-style query language for SQL engines | B•Solid | 75.6 | 92.5% | - |
| #4 | sbt/sbt4,946 sbt, the interactive build tool | S•Elite | 74.6 | 88.8% | 1 |
| #5 | The Anorm database library | S•Elite | 74.3 | 90.7% | - |
| #6 | akka/alpakka-kafka1,422 Alpakka Kafka connector - Alpakka is a Reactive Enterprise Integration library for Java and Scala, based on Reactive Streams and Akka. | S•Elite | 74.1 | 100.0% | - |
| #7 | ECMAScript Specification (ECMA-262) Metalanguage | S•Elite | 73.9 | 100.0% | - |
| #8 | sbt/sbt-site176 Site generation for sbt | S•Elite | 73.9 | 100.0% | - |
| #9 | gitbucket/gitbucket9,401 A Git platform powered by Scala with easy installation, high extensibility & GitHub API compatibility | S•Elite | 72.5 | 91.4% | - |
| #10 | The Streaming-first HTTP server/module of Apache Pekko | S•Elite | 72.1 | 85.8% | - |
| #11 | Add-on module for Jackson (https://github.com/FasterXML/jackson) to support Scala-specific datatypes | B•Solid | 71.6 | 91.7% | 1 |
| #12 | Netflix/atlas3,562 In-memory dimensional time series database. | S•Elite | 70.5 | 95.1% | - |
| #13 | Functional programming with Kafka and Scala | B•Solid | 70.4 | 95.7% | - |
| #14 | scalatra/scalatra2,650 Tiny Scala high-performance, async web framework, inspired by Sinatra | A•Welcoming | 70.0 | 89.5% | - |
| #15 | Neo4j Connector for Apache Spark, which provides bi-directional read/write access to Neo4j from Spark, using the Spark DataSource APIs | A•Welcoming | 69.7 | 82.3% | - |
| #16 | A release plugin for sbt | B•Solid | 69.7 | 95.2% | - |
| #17 | Splice repository | A•Welcoming | 69.7 | 85.3% | 3 |
| #18 | :robot: A bot that helps you keep your projects up-to-date | A•Welcoming | 69.4 | 85.5% | 1 |
| #19 | Vyxal/Vyxal302 A code-golfing language experience that has aspects of traditional programming languages - terse yet convenient. | B•Solid | 69.4 | 90.0% | - |
| #20 | A platform of libraries for Scala 3 | B•Solid | 69.4 | 96.3% | - |
| #21 | Essential Building Blocks for Scala | B•Solid | 69.3 | 91.7% | - |
| #22 | A python-ish pure and total functional programming language | B•Solid | 68.5 | 84.6% | - |
| #23 | Doctest for scala | B•Solid | 68.3 | 96.7% | - |
| #24 | Deterministic, AI-driven development flows. | B•Solid | 68.3 | 98.6% | - |
| #25 | Rudder is a configuration and security automation platform. Manage your Cloud, hybrid or on-premises infrastructure in a simple, scalable and dynamic way. | A•Welcoming | 68.1 | 86.7% | - |
| #26 | Scalate is a Scala based template engine which supports HAML, Mustache and JSP, Erb and Velocity style syntaxes. | B•Solid | 67.8 | 92.1% | - |
| #27 | scala-js/scala-js4,710 Scala.js, the Scala to JavaScript compiler | A•Welcoming | 67.5 | 86.5% | - |
| #28 | scalameta/scalameta1,155 Library to read, analyze, transform and generate Scala programs | A•Welcoming | 67.2 | 90.2% | - |
| #29 | Human-AI Collaborative Data Science Using Visual Workflows | A•Welcoming | 67.2 | 81.9% | - |
| #30 | The LibreCaptcha framework, for self-hosted, privacy respecting CAPTCHAs | B•Solid | 67.0 | 83.9% | - |
| #31 | chipsalliance/chisel4,766 Chisel: A Modern Hardware Design Language | A•Welcoming | 66.9 | 82.2% | - |
| #32 | Server-side Web Authentication library for Java https://www.w3.org/TR/webauthn/#rp-operations | B•Solid | 66.5 | 100.0% | - |
| #33 | filodb/FiloDB1,467 Distributed Prometheus time series database | A•Welcoming | 66.2 | 87.4% | - |
| #34 | A language with lexical effect handlers and lightweight effect polymorphism | A•Welcoming | 65.9 | 70.6% | 2 |
| #35 | Mutation testing for Scala | A•Welcoming | 65.9 | 94.4% | - |
| #36 | apache/pekko1,626 Build highly concurrent, distributed, and resilient message-driven applications using Java/Scala | A•Welcoming | 65.8 | 87.0% | - |
| #37 | slick/slick2,664 Slick (Scala Language Integrated Connection Kit) is a modern database query and access library for Scala | A•Welcoming | 65.6 | 75.9% | - |
| #38 | Yet another Typesafe config Scala wrapper powered by circe | B•Solid | 65.0 | 76.3% | - |
| #39 | Cross-platform compilation support for sbt. | A•Welcoming | 65.0 | 75.0% | - |
| #40 | An sbt plugin for Flyway database migration | A•Welcoming | 65.0 | 92.6% | - |
| #41 | A toolkit for servicing HTTP requests in Scala | B•Solid | 64.9 | 100.0% | - |
| #42 | scalameta/scalafmt1,488 Code formatter for Scala | A•Welcoming | 64.6 | 93.4% | 1 |
| #43 | The code examples used in Programming Scala, 2nd and 3rd Editions (O'Reilly) | B•Solid | 64.4 | 97.1% | - |
| #44 | experimental CPS transformer for dotty | B•Solid | 64.2 | 100.0% | - |
| #45 | nasa/fpp113 F Prime Prime: A modeling language for F Prime | A•Welcoming | 64.2 | 85.1% | - |
| #46 | sbt plugin to create a class diagram | B•Solid | 64.0 | 100.0% | - |
| #47 | Clickhouse Scala Client with Reactive Streams support | A•Welcoming | 63.9 | 78.7% | - |
| #48 | The MLscript programming language. Functional and object-oriented; structurally typed and sound; with powerful type inference. Soon to have full interop with TypeScript! | A•Welcoming | 63.6 | 86.5% | - |
| #49 | Gobra is an automated, modular verifier for Go programs, based on the Viper verification infrastructure. | A•Welcoming | 63.6 | 75.4% | - |
| #50 | Declarative text based tool for data analysts and engineers to extract, load, transform and orchestrate their data pipelines. | B•Solid | 63.5 | 94.1% | - |
How to Get Your Scala PR Merged
1
Check C-Rankâ„¢ 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: Scala Open Source
What is the most welcoming Scala open-source repository?
The highest-ranked Scala repository on GetMerged is currently yaes-io/yaes, with a C-Rank score of 76.3/100 and a 100.0% PR merge rate.
How can I find good first issues in Scala?
You can browse verified beginner-friendly issues in Scala by visiting our curated Good First Issues directory at getmerged.abhishekco.de/good-first-issue/scala.
What makes a Scala repository ‘Super Welcoming’ on GetMerged?
A ‘Super Welcoming’ (S-Tier) Scala 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.