Each one is WebAssembly run by crc's own interpreter. It says what it may read and change, crc shows you before you install it, and holds it to that after. No files, no network, no other programs.
A manifest lists what the extension may touch. Anything it did not ask for is not even linked in.
It runs off the main thread with a time and memory budget, and gets only the text you give it.
Official extensions are built from source in CI and signed; crc checks the signature and every checksum.
In crc: Extensions › Extensions… (⌘⇧X), pick one, Install. The signed registry opens with its first published release; until then these install from a folder.
Change the case of the selection or document: upper, lower, title, snake_case, kebab-case, camelCase, PascalCase and CONSTANT_CASE.
Base64, URL and HTML encoding of the selection or document, both ways.
Sort the selected lines, or the whole document, and remove duplicates.
The scaffold asks for the name, description, icon and commands, and writes an extension that builds and installs as it is. Everything in crc-extensions is MIT or Apache 2.0, so yours can use any licence.
The full guide →
# in a clone of crc-extensions
python3 scripts/new-extension.py
cargo build --release \
--target wasm32-unknown-unknown
# then in crc: Install from Folder…Why WebAssembly, why crc's own interpreter, and how signing works: the extensions design →