CASL
Isomorphic authorization: define what each user may do, check it anywhere.
Auth and security libraries npm MIT
How CASL is used
CASL joined the catalog on its public numbers (993,826 downloads a week on npm and 7,103 GitHub stars), not on our project count: it is a dependency in 12 public GitHub projects of our scan, 7 of them set up for AI coding agents. Projects that use it most often also use ts-node (75.0%), Prettier (75.0%), Jest (66.7%).
CASL popularity over time
Gid Score 47: downloads 64, use in agent projects 20, GitHub stars 44, downloads trend 58 (each 0-100). How it is calculated.
Often used with CASL
| ts-node | 75.0% of CASL projects · 15.7× more than average |
|---|---|
| Prettier | 75.0% of CASL projects · 3.6× more than average |
| Jest | 66.7% of CASL projects · 10.5× more than average |
| NestJS | 58.3% of CASL projects · 109.7× more than average |
| RxJS | 58.3% of CASL projects · 27.6× more than average |
| ESLint | 91.7% of CASL projects · 2.5× more than average |
| dotenv | 58.3% of CASL projects · 3.7× more than average |
| bcrypt (JavaScript) | 50.0% of CASL projects · 48.5× more than average |
By coding agent
| Claude Code | 0.2% of projects set up for it |
|---|
Share of public repos configured for each agent that list CASL as a dependency.
How CASL is funded
Open Collective: CASL
| Received, last 12 months | $415 Oct 2025 – Sep 2026 |
|---|---|
| Estimated annual budget | $479 Open Collective's estimate |
| Balance | $1,238 |
| Raised since the start | $2,342 · $1,104 paid out |
| Typical month median, last 12 months | $1 · $2 over 24 months |
| Last 12 months vs the 12 before | -30% |
| Contributors, last 12 months | 4 |
Top company backers all time
| Sight & Sound | $700 since Jan 2025 |
|---|---|
| Gathering Solutions OÜ | $40 since Feb 2020 |
Oct 2021Sep 2026
Money by month, last five years. First money received in Feb 2020. The typical month is the median: one big one-off donation does not move it.
USD after payment processor fees, as Open Collective reports it; fiscal host Open Source Collective. Source
Ways to fund CASL
Patreon Open Collective Own page
As the maintainers list them in FUNDING.yml on GitHub and in the npm package. Checked Oct 20, 2026.
Install
| Package | npm install @casl/ability |
|---|---|
| Main stacks | TypeScript / JavaScript (9), Next.js (2), PHP (1) |
| Example projects | meta-d/ocap, databayt/hogwarts |
Alternatives to CASL
In our scan, none of the most used tools in Auth and security libraries does the same job as CASL: they are add-ons, companions or tools for a different task.
More in Auth and security libraries: bcryptjs NextAuth.js jsonwebtoken cryptography PyJWT jose Better Auth Helmet