While it may be true that pylance is closed source and vscode specific, pyright[1] is MIT. Pylance does appear to still be a language server as well. As far as I know, most language plugins still use LSP, including Typescript/Javascript, Rust, and Go.
[1] https://github.com/microsoft/pyright
In Batteries included with Emacs (2020)microsoft
pyright
Python2019–2025
microsoft / pyright
pyright
Static Type Checker for Python
62Distinct people
68Mentions
0Explicit recommenders
15.7KGitHub stars
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What it is
Static Type Checker for Python
GitHub
Where it is used
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Also in these discussions
- google/pytype · linked in 6 of the same discussions
- python/mypy · linked in 5 of the same discussions
- meta/pyre-check · linked in 3 of the same discussions
Mentioned in the same Hacker News threads. That is not proof they are substitutes.
This week on Hacker News
Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 2:59:58 PM UTC.
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Mentions over time
HN mentions by year68 dated mentions
Observed mentions: 2019-03-24 01:55:38 UTC to 2025-12-22 22:51:45 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 2 | 1 | 1 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 5 | 0 | 5 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 15 | 0 | 15 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 14 | 1 | 13 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 16 | 2 | 14 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 5 | 1 | 4 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 11 | 0 | 11 |
From the project README
An excerpt from the repository, fetched Nov 13, 2026.
Read the project’s introduction
Static Type Checker for Python
Pyright is a full-featured, standards-based static type checker for Python. It is designed for high performance and can be used with large Python source bases.
Pyright includes both a command-line tool and an extension for Visual Studio Code.
Pyright Playground
Try Pyright in your browser using the Pyright Playground.
Documentation
Refer to the documentation for installation, configuration, and usage details.
Performance
The weekly type checker benchmark compares Pyright with other Python type checkers.
The Pyright release history tracks per-package execution time and peak memory across releases.
Environment variables
If Pyright fails to create a temporary directory (for example in remote/server environments where the OS temp directory doesn't exist or isn't writable), you can override the temp directory root:
PYRIGHT_TMPDIR: Absolute path to a directory that Pyright can use for temporary files/directories. Pyright will create it if needed.
Pyright otherwise relies on the platform temp directory (for example TMPDIR, TMP, TEMP, or the OS default).
Community
Do you have questions about Pyright or Python type annotations in general? Post your questions in the discussion section.
If you would like to report a bug or request an enhancement, file a new issue in either the pyright or pylance-release issue tracker. In general, core type checking functionality is associated with Pyright while language service functionality is associated with Pylance, but the same contributors monitor both repos. For best results, provide the information requested in the issue template.
Contributing
This project welcomes contributions and suggestions. For feature and complex bug fix contributions, it is recommended that you first discuss the proposed change with Pyright’s maintainers before submitting the pull request. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.
When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.
This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.
Read the full README on GitHubWhat Hacker News says
15 sourcesCheck out https://github.com/microsoft/pyright, it's pretty snappy if you don't mind some JS in your ecosystem.
In Twelve Years of GoWell there is Pyright by MS (that's what Pylance is based on) and python-language-server by MS - that one has been superseded by Pyright and is deprecated in Code.
https://github.com/microsoft/pyright
https://github.com/Microsoft/python-language-server
The only(?) one not by MS is Jedi:
https://github.com/pappasam/jedi-language-server
In Can we trust Microsoft with open source?Thanks to the maintainer's great responsiveness, Pyright will implement such a warning soon: https://github.com/microsoft/pyright/issues/2308
In Python Anti-PatternIndeed, when I asked for potential solutions, I thought it would be ... weird, to evaluate default args at call time, but it turns out that many other languages are like that[0], and the wierdness was my subjective perception shaped by my Python-heavy background.
Regarding breaking backward compatibility in a future release, I'm not qualified to weigh in on the design decision of balancing between the disadvantages of breaking backward compatibility and the advantage of more intuitive semantics.
[0] https://github.com/microsoft/pyright/discussions/2306#discus...
In Python Anti-PatternYou're right, I checked, and pyright only warns about function calls in default arguments, not mutable containers.
I started a discussion in Pyright's repo here[0].
[0] https://github.com/microsoft/pyright/discussions/2306
In Python Anti-PatternLast I checked, most of the MS-owned language servers used proprietary licenses.
An example is the Python language server
https://github.com/microsoft/pylance-release
They base it 90% on the open-source pyright library. Then the lock down all their own enhancements.
https://github.com/microsoft/pyright
This is why MIT isn't always the correct choice. GPL wouldn't hurt devs at all and would protect from this kind of garbage from MS.
In Web-based editorYep, but not secret, it's the in-progress dataclass_transform draft spec, already implemented in (open source) Pyright, and Pylance re-uses Pyright, so it gets that support.
https://github.com/microsoft/pyright/blob/main/specs/datacla...
In SQLModel – SQL Databases in FastAPIYep it uses the in-progress draft-spec dataclass_transforms https://github.com/microsoft/pyright/blob/main/specs/datacla...
As Pyright already supports it, and Pylance is built on Pyright, they can use it directly. Hopefully more editors will use it and hopefully it will be part of the standard Python (in a PEP, with typing.dataclass_transform, and with mypy support).
And just in case you're wondering, there's no downside to having the dataclass_transform, anything that doesn't support it is unaffected, and nothing else would have completion either way.
In SQLModel – SQL Databases in FastAPIThey've invested a ton into Python support in VSCode in recent years. It's really good.
The language server Microsoft built for type checking and completion (https://github.com/microsoft/pyright) is excellent. It makes Python feel like a first-class statically typed language, which isn't something I was able to replicate in Pycharm (tried this very recently). Meanwhile, it's just baked into VSCode, no configuration needed.
I use Jetbrains tools for several languages, but for Python and frontend (Typescript with React/Vue/Angular) VSCode is hitting the perfect notes.
In Python Best Practices for a New Project in 2021The Pyright typechecker for Python (a Mypy alternative): https://github.com/microsoft/pyright
In A curated list of JavaScript tooling not written in JavaScriptReminds me of Pyright - a static type checker for Python, written in TypeScript.
https://github.com/microsoft/pyright
In A curated list of JavaScript tooling not written in JavaScriptIt's important to understand that the type systems for Python are not really an inherent feature of Python, but the systems enforced by each of the static checkers (which tend to adopt each other's advancements and drive syntactic support into the core system of annotations, so there's a common baseline advancing with the individual systems). A recent advancement in one of those type systems would be pylance (actually pyright, since that's the typechecker for the pylance language server) support for higher-kinded type variables [0]. Mypy, I believe, has identified this as a thing to support, too.
An example of an improvement in annotations specifically to enable type system improvements that require supporting syntax improvement is PEP 646 support for Variadic Generics. [1] Even though it is in draft, pyright has already landed support fo
Read the rest
r it for the type system improvements motivating it. [2]
[0] item #4, https://devblogs.microsoft.com/python/pylance-introduces-fiv...
[1] https://www.python.org/dev/peps/pep-0646/
[2] https://github.com/microsoft/pyright/releases/tag/1.1.107
This title is inaccurate.
The language server _is_ open source, and is available here: https://github.com/microsoft/python-language-server. This is the default one VSCode ships with.
This issue is filed on Pylance, a new (released June 2020) language server that's currently still in beta (announcement: https://devblogs.microsoft.com/python/announcing-pylance-fas...).
Also, like the contributor notes, a lot of the "secret sauce" in Pylance is part of the open source Pyright typechecker: https://github.com/microsoft/pyright.
In Microsoft Refuses to Open Source VSCode Python Language ServerPylance is built on their open source Pyright library, which is also available as a VSCode extension. I'm just using Pyright instead and don't seem to be missing out on anything important.
https://github.com/microsoft/pyright
In Microsoft Refuses to Open Source VSCode Python Language Server