Sanitize ops

Updated Oct 19, 2026 v0.1.4

Sanitize ops change a value before the validate ops see it. This page lists the 23 built-in sanitize ops. You write them in the sanitize(...) group of a derive string, as in "sanitize(trim, downcase)". A sanitize op never reports an error. An op that works on strings or lists returns any other kind of value unchanged. The HTML ops use the html_sanitize_ex package, which GuardedStruct depends on.

Text

Op	Works on	Effect
`trim`	Strings	Removes leading and trailing whitespace with `String.trim/1`.
`upcase`	Strings	Upper-cases with `String.upcase/1`.
`downcase`	Strings	Lower-cases with `String.downcase/1`.
`capitalize`	Strings	Capitalizes with `String.capitalize/1`. `"hello WORLD"` becomes `"Hello world"`.
`squish`	Strings	Collapses every run of whitespace, including newlines, into one space and trims the ends. `" a b \n c "` becomes `"a b c"`.
`no_control`	Strings	Removes ASCII control characters: U+0000 to U+0008, U+000B, U+000C, U+000E to U+001F and U+007F. Tab, line feed and carriage return stay.
`no_zero_width`	Strings	Removes the zero-width characters U+200B, U+200C, U+200D, U+FEFF and U+2060.
`rich_text_safe`	Strings	Applies `no_zero_width`, then `no_control`.

HTML

Op	Works on	Effect
`strip_tags`	Strings	Removes every tag with `HtmlSanitizeEx.strip_tags/1`. `"<p>Hi <b>there</b></p>"` becomes `"Hi there"`.
`basic_html`	Strings	Cleans the string with `HtmlSanitizeEx.basic_html/1`.
`html5`	Strings	Cleans the string with `HtmlSanitizeEx.html5/1`.
`markdown_html`	Strings	Cleans the string with `HtmlSanitizeEx.markdown_html/1`.
`tag=op`	Strings	Trims, applies the sanitize op named after the equals sign, and trims again. `tag=strip_tags` turns `" <p>Hi</p> "` into `"Hi"`.

Numbers

Op	Works on	Effect
`string_float`	Strings	Strips tags, then reads the start of the string with `Float.parse/1`. `"3.14abc"` becomes `3.14`. A string with no number becomes `0.0`.
`string_integer`	Strings	Strips tags, then reads the start of the string with `Integer.parse/1`. `"42abc"` becomes `42`. A string with no number becomes `0`.
`clamp=[min, max]`	Numbers	Moves a number below `min` up to `min` and a number above `max` down to `max`. `clamp=[0, 100]` turns `150` into `100`.

Lists and defaults

Op	Works on	Effect
`uniq`	Lists	Removes duplicates with `Enum.uniq/1`.
`compact`	Lists	Removes `nil` items only.
`reject_empty`	Lists	Removes `nil`, `""`, `[]` and `%{}` items.
`sort`	Lists	Sorts with `Enum.sort/1`.
`each=[ops]`	Lists	Applies the inner sanitize ops, in order, to every item.
`default_when_nil=value`	Any	Replaces `nil` with the value. It also fills a field that is `nil` or missing, and then the derive string runs on the value. Every other op skips a `nil` field.
`default_when_empty=value`	Any	Replaces `nil`, `""`, `[]` and `%{}` with the value. `default_when_empty="anonymous"` turns `""` into `"anonymous"`. A field that is `nil` is skipped, so on a field this op replaces the empty values only. A `nil` item inside `each=[...]` is replaced too.

Call an op directly

Each op is also a function. The value comes first, so calls pipe.

elixir

alias GuardedStruct.Derive.SanitizerDerive

"  Hello  "
|> SanitizerDerive.sanitize(:trim)
|> SanitizerDerive.sanitize(:downcase)
# "hello"

SanitizerDerive.sanitize(150, {:clamp, [0, 100]})
# 100