Penify.dev vs Swimm

Two fact sheets from our own research, side by side — pricing, platforms, API access and status re-checked by us rather than quoted from the vendors.

The short answer

Free plan: Penify.dev has one; Swimm prices on request
Higher Trust score: Swimm — 88 vs 81 for Penify.dev
Best fit: Penify.dev: Teams that want docstrings kept current automatically as pull requests land · Swimm: Teams documenting a mainframe or legacy .NET/Java estate before a migration
Platforms: Penify.dev: Web · Swimm: Web, VS Code extension
Status: Both up at our last check — Penify.dev Oct 15, 2026, Swimm Oct 16, 2026

From our own records as of each tool's last check. Anything we have not confirmed is left out rather than guessed. How we verify

Penify.devWrites docstrings and inline documentation from your code changes via CLI, git hook, or GitHub App.

SwimmStatic analysis plus AI that reads legacy code and writes the documentation and diagrams a migration team needs.

Side by side

Fact	Penify.dev	Swimm
Category	Documentation Generators	Documentation Generators
Pricing model	Freemium	Contact
Starts at	$18/mo	—
Trust score	81 / 100	88 / 100
Platforms	Web	Web, VS Code extension
Company	Penify.dev	Swimm
Launched	—	2019
Last verified	Oct 15, 2026	Oct 16, 2026

What our research says

Penify.dev

Penify.dev focuses narrowly on the least glamorous documentation task — writing docstrings for the functions inside a diff — instead of trying to generate whole READMEs or wikis. That focus makes it easy to bolt onto an existing pull-request workflow, but it also means it does not replace higher-level documentation tools, and the free tier's per-file cap on private repos pushes active teams toward a paid plan quickly.

Pros

Comments directly on pull requests through a GitHub App instead of requiring a separate tool to check
Works via CLI or git hook for teams that don't want a GitHub-specific integration
Free tier is usable for public repositories without a credit card

Cons

Private repo usage on the free tier is capped by file count, which active codebases will exceed quickly
Limited to a fixed set of supported languages rather than open-ended code coverage
Only documents inline code, not higher-level architecture or user-facing docs

Swimm

Swimm is the rare documentation tool that treats old code as the source of truth instead of asking humans to describe it. If you are staring at a COBOL or .NET estate nobody understands, the flow maps and extracted business rules are the useful part. The catch is that it is no longer a tool you can simply buy: it is a staged engagement with engineers attached, and the self-serve documentation product it was known for is not what the site sells today.

Pros

Deterministic static analysis backs the AI output, so traces come from the code rather than a guess
Produces diagrams and flow maps, not only prose
Covers mainframe and COBOL alongside .NET and Java
Work is broken into fixed-price stages you can stop after

Cons

No pricing published anywhere on the site
Repositioned away from the continuous-documentation product it was known for
Aimed at large estates, which makes it overkill for a normal repository

Which one fits

Choose Penify.dev if you need

Teams that want docstrings kept current automatically as pull requests land
Open source maintainers documenting public repositories for free
Developers who prefer a git hook or CLI over a separate documentation dashboard

Choose Swimm if you need

Teams documenting a mainframe or legacy .NET/Java estate before a migration
Architects who need job-flow and variable traces out of unfamiliar code
Enterprises that want non-engineers to read what the code actually does