ChmodCalc provides permission-conversion tools and educational content for general informational purposes. Here’s what that means in practice.

A calculator, not a guardrail

The modes and commands this site shows are correct to the best of our knowledge against GNU coreutils chmod — but running them is your decision. chmod applied to the wrong file, the wrong class or with a stray -R can lock you out of your own data, break a deployed site, or quietly open a security hole. Verify the expansion the calculator shows — that’s what it’s for — and test on a copy or a non-production path when the change matters.

Platforms genuinely differ

chmod is standardized up to a point, then diverges: GNU/Linux, macOS/BSD, busybox and Solaris disagree at the edges — the sticky bit under o=/o+t, X on unusual targets, mandatory locking under setgid-without-x, what a= clears. The site follows GNU conventions and calls out known divergences in the special-bits guide, but the authority is always the chmod on the machine you’re administering. When in doubt, man chmod there wins.

Security guidance is general, not a review

Articles like common chmod mistakes describe typical patterns and risks. They are not a security audit of your system: threat models differ, hosting environments differ, and “the right permissions” for a hobby VM and a payment server are different answers. For regulated or high-stakes environments, get advice scoped to your actual setup.

Advertising

The site may display third-party advertising (for example Google AdSense) to cover hosting costs. Advertisers don’t influence what the calculator outputs or what the guides recommend.

Liability

To the maximum extent permitted by law, ChmodCalc and its maintainers are not liable for losses arising from use of this site or reliance on its output — including lockouts, broken deployments and security incidents. When permissions matter, confirm them on the target system.