--- /dev/null
+# function-url-scheme-blacklist
+
+Specify a blacklist of disallowed URL schemes.
+
+```css
+a { background-image: url('http://www.example.com/file.jpg'); }
+/** ↑
+ * This URL scheme */
+```
+
+A [URL scheme](https://url.spec.whatwg.org/#syntax-url-scheme) consists of alphanumeric, `+`, `-`, and `.` characters. It can appear at the start of a URL and is followed by `:`.
+
+This rule treats URL schemes as case insensitive (`https` and `HTTPS` are the same).
+
+This rule ignores URL arguments without an existing URL scheme.
+
+This rule ignores URL arguments with variables or variable interpolation (`$sass`, `@less`, `--custom-property`, `#{$var}`, `@{var}`, `$(var)`).
+
+## Options
+
+`array|string|regex`: `["array", "of", "schemes" or "regex"]|"scheme"|/regex/`
+
+Given:
+
+```js
+["ftp", "/^http/"]
+```
+
+The following patterns are considered violations:
+
+```css
+a { background-image: url('ftp://www.example.com/file.jpg'); }
+```
+
+```css
+a { background-image: url('http://www.example.com/file.jpg'); }
+```
+
+```css
+a { background-image: url('https://www.example.com/file.jpg'); }
+```
+
+The following patterns are *not* considered violations:
+
+```css
+a { background-image: url('data:image/gif;base64,R0lGODlhAQABAIAAAAUEBAAAACwAAAAAAQABAAACAkQBADs='); }
+```
+
+```css
+a { background-image: url('example.com/file.jpg'); }
+```
+
+```css
+a { background-image: url('/example.com/file.jpg'); }
+```
+
+```css
+a { background-image: url('//example.com/file.jpg'); }
+```
+
+```css
+a { background-image: url('./path/to/file.jpg'); }
+```