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 • Thu, 15 Oct 2026 UTC
Tracked Repos
1,241
>100 stars verified
Avg Merge Rate
73%
90-day external PRs
Open GFIs
119
Beginner friendly issues
Welcoming Tier
50
S & A Tier maintainers
Ranked Scala Repositories
Showing top 50 of 1,241 ranked repositories
| Rank | Repository | Tier | Score | Merge Rate | Good First Issues |
|---|---|---|---|---|---|
| #1 | Splice repository | S•Elite | 73.5 | 81.1% | 5 |
| #2 | filodb/FiloDB1,468 Distributed Prometheus time series database | S•Elite | 70.7 | 86.7% | - |
| #3 | Apache DataFusion Comet Spark Accelerator | S•Elite | 70.1 | 64.0% | 23 |
| #4 | joernio/joern3,573 Open-source code analysis platform for C/C++/Java/Binary/Javascript/Python/Kotlin based on code property graphs. Discord https://discord.gg/vv4MH284Hc | S•Elite | 69.9 | 86.9% | - |
| #5 | The Streaming-first HTTP server/module of Apache Pekko | A•Welcoming | 69.7 | 79.5% | - |
| #6 | llm4s/llm4s269 Agentic and LLM Programming in Scala | A•Welcoming | 69.3 | 47.8% | 76 |
| #7 | sbt/sbt4,954 sbt, the interactive build tool | S•Elite | 68.4 | 85.9% | 1 |
| #8 | guardian/frontend5,898 The Guardian DotCom. | A•Welcoming | 67.9 | 77.3% | - |
| #9 | 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 | 67.0 | 83.7% | - |
| #10 | NVIDIA/cudf-spark1,011 NVIDIA cuDF for Apache Spark plugin - accelerate Apache Spark with GPUs | A•Welcoming | 66.5 | 69.3% | - |
| #11 | scalameta/scalameta1,158 Library to read, analyze, transform and generate Scala programs | A•Welcoming | 66.2 | 81.6% | - |
| #12 | apache/gluten1,605 Gluten is a middle layer responsible for offloading JVM-based SQL engines' execution to native engines. | A•Welcoming | 66.1 | 59.9% | 4 |
| #13 | Neo4j Connector for Apache Spark, which provides bi-directional read/write access to Neo4j from Spark, using the Spark DataSource APIs | A•Welcoming | 66.1 | 80.0% | - |
| #14 | :robot: A bot that helps you keep your projects up-to-date | A•Welcoming | 65.9 | 76.4% | - |
| #15 | lichess-org/lila18,830 ♞ lichess.org: the forever free, adless and open source chess server ♞ | A•Welcoming | 65.9 | 75.1% | 1 |
| #16 | Human-AI Collaborative Data Science Using Visual Workflows | A•Welcoming | 65.6 | 79.9% | - |
| #17 | softwaremill/tapir1,476 Rapid development of self-documenting APIs | A•Welcoming | 65.4 | 82.7% | - |
| #18 | chipsalliance/chisel4,809 Chisel: A Modern Hardware Design Language | A•Welcoming | 65.1 | 80.0% | - |
| #19 | scalameta/metals2,333 Scala language server with rich IDE features 🚀 | A•Welcoming | 64.5 | 75.5% | - |
| #20 | getkyo/kyo819 Toolkit for Scala Development | A•Welcoming | 64.3 | 50.0% | 4 |
| #21 | scala/scala36,319 The Scala 3 compiler, also known as Dotty. | A•Welcoming | 64.0 | 71.2% | - |
| #22 | delta-io/delta9,044 An open-source storage framework that enables building a Lakehouse architecture with compute engines including Spark, PrestoDB, Flink, Trino, and Hive and APIs | A•Welcoming | 63.9 | 58.7% | 1 |
| #23 | scalameta/scalafmt1,490 Code formatter for Scala | A•Welcoming | 63.3 | 88.2% | 1 |
| #24 | apache/pekko1,650 Build highly concurrent, distributed, and resilient message-driven applications using Java/Scala | A•Welcoming | 63.3 | 83.3% | - |
| #25 | akka/akka-core13,280 A platform to build and run apps that are elastic, agile, and resilient. SDK, libraries, and hosted environments. | A•Welcoming | 63.2 | 76.9% | - |
| #26 | gitbucket/gitbucket9,402 A Git platform powered by Scala with easy installation, high extensibility & GitHub API compatibility | A•Welcoming | 63.1 | 87.1% | - |
| #27 | State of the Art Natural Language Processing | A•Welcoming | 63.0 | 66.7% | - |
| #28 | microsoft/SynapseML5,245 Simple and Distributed Machine Learning Python Library porting ML algorithms for Spark | A•Welcoming | 63.0 | 72.2% | - |
| #29 | Scala CLI is a command-line tool to interact with the Scala language. It lets you compile, run, test, and package your Scala code (and more!) | A•Welcoming | 62.7 | 70.9% | - |
| #30 | The Community Maintained High Velocity Web Framework For Java and Scala. | A•Welcoming | 62.6 | 76.7% | - |
| #31 | Definition of the Viper intermediate verification language. | A•Welcoming | 62.4 | 76.5% | - |
| #32 | Declarative text based tool for data analysts and engineers to extract, load, transform and orchestrate their data pipelines. | A•Welcoming | 62.3 | 89.6% | - |
| #33 | com-lihaoyi/mill2,797 A better build tool for Java, Scala and Kotlin: Simpler than Maven, easier than Gradle, with 3-7x faster dev workflows than other JVM build tools | A•Welcoming | 62.1 | 55.2% | - |
| #34 | Open-source high-performance RISC-V processor | A•Welcoming | 62.0 | 60.4% | - |
| #35 | Refactoring and linting tool for Scala | A•Welcoming | 62.0 | 72.7% | 2 |
| #36 | ACINQ/eclair1,347 A scala implementation of the Lightning Network. | A•Welcoming | 62.0 | 70.0% | - |
| #37 | Lichess' websocket server | A•Welcoming | 61.8 | 75.0% | - |
| #38 | Build type-safe, boilerplate-less MCP servers and clients in Scala | A•Welcoming | 61.7 | 80.5% | - |
| #39 | simple combinator-based parsing for Scala. formerly part of the Scala standard library, now a separate community-maintained module | A•Welcoming | 61.6 | 53.8% | - |
| #40 | The Scala Package Index | A•Welcoming | 61.5 | 28.9% | 1 |
| #41 | A language with lexical effect handlers and lightweight effect polymorphism | A•Welcoming | 61.3 | 68.4% | - |
| #42 | slick/slick2,665 Slick (Scala Language Integrated Connection Kit) is a modern database query and access library for Scala | A•Welcoming | 61.3 | 69.8% | - |
| #43 | locationtech/geomesa1,499 GeoMesa is a suite of tools for working with big geo-spatial data in a distributed fashion. | A•Welcoming | 61.2 | 94.5% | - |
| #44 | Like VexRiscv, but, Harder, Better, Faster, Stronger | A•Welcoming | 61.2 | 72.0% | - |
| #45 | ECMAScript Specification (ECMA-262) Metalanguage | A•Welcoming | 61.2 | 92.3% | - |
| #46 | Gobra is an automated, modular verifier for Go programs, based on the Viper verification infrastructure. | A•Welcoming | 61.2 | 80.4% | - |
| #47 | softwaremill/sttp1,506 The Scala HTTP client you always wanted! | A•Welcoming | 61.1 | 80.9% | - |
| #48 | Apache Daffodil | A•Welcoming | 61.1 | 52.8% | - |
| #49 | 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 | 61.1 | 82.7% | - |
| #50 | The standard Scala XML library | A•Welcoming | 61.0 | 48.0% | - |
How to Get Your Scala 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: Scala Open Source
What is the most welcoming Scala open-source repository?
The highest-ranked Scala repository on GetMerged is currently canton-network/splice, with a C-Rank score of 73.5/100 and a 81.1% 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.