> For the complete documentation index, see [llms.txt](https://docs.feedotter.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.feedotter.com/set-up-your-own-template/advanced-template-information/filters.md). # Filters Custom and built-in Twig filters available inside FeedOtter email templates. All tokens use \[\[ ]] for output and \[% %] for logic blocks. **Basic syntax:** ``` [[ variable | filterName ]] [[ variable | filterName(arg1, arg2) ]] [[ variable | filterName(anotherVariable) ]] ``` *** ### Working with Dates FeedOtter can use any date format supported by PHP. Full reference: The most common date variable is `feedotter.send_date_object`, which represents the scheduled send date of the campaign. ``` [[feedotter.send_date_object | date('F j, Y')]] // September 21, 2022 [[feedotter.send_date_object | date('F d')]] // September 21 [[feedotter.send_date_object | date('M. j, Y')]] // Sep. 21, 2022 [[feedotter.send_date_object | date('d-m-y')]] // 21-09-22 [[feedotter.send_date_object | date('l, F j, Y')]] // Wednesday, September 21, 2022 [[feedotter.send_date_object | date('D, F j, Y')]] // Wed, Sep. 21, 2022 [[feedotter.send_date_object | date('F Y')]] // September 2022 [[feedotter.send_date_object | date('n/j/Y')]] // 9/21/2022 ``` To render the date in a specific timezone, pass the timezone as a second argument to `date()`: ``` [[feedotter.send_date_object | date('g:i A T', 'America/Los_Angeles')]] // 9:00 AM PDT [[feedotter.send_date_object | date('F j, Y', 'America/Chicago')]] // September 21, 2022 ``` You can also convert the timezone first using `switch_timezone` and then format: ``` [[feedotter.send_date_object | switch_timezone('America/New_York') | date('l, F j, Y')]] ``` *** ### Custom Filters #### `linkColor` Finds all `` tags in an HTML string and injects an inline `color` style, overriding any existing color declaration. Passes through plain text (no HTML) unchanged. | Argument | Type | Description | | -------- | ------ | --------------------------------------------------------------- | | `color` | string | Hex color value. Accepts `#RRGGBB`, `RRGGBB`, `#RGB`, or `RGB`. | ``` [[ custom.body | linkColor('#c0392b') ]] [[ custom.body | linkColor(custom.linkColor) ]] ``` Output on each anchor: `style="color: #c0392b !important;"` > If the `` tag already has a `style` attribute, the new color is appended and any prior `color` declaration is removed. *** #### `resize` Rewrites an image URL to pass through the FeedOtter resize proxy at the specified dimensions. | Argument | Type | Required | Description | | --------- | ------ | -------- | ------------------------------------------------ | | `width` | int | Yes | Target width in pixels. | | `height` | int | No | Target height in pixels. | | `overlay` | string | No | Overlay identifier passed to the resize service. | ``` [[ post.image_url | resize(500) ]] [[ post.image_url | resize(500, 300) ]] ``` *** #### `cleanImages` Strips `width` and `height` attributes (both HTML attributes and inline style values) from all `` tags, then adds `width="100%"` to any image that has no width set. Useful when displaying raw HTML content in an email. ``` [[ post.post_content | cleanImages ]] ``` **Common use case — rendering raw CMS HTML:** ``` [[ post.post_content | striptags('


') | cleanImages ]] ``` *** #### `regex_replace` Runs a PHP `preg_replace` on a string. Gives full control over substitution using regular expressions. | Argument | Type | Required | Description | | ------------- | ------ | -------- | ----------------------------------------------------------- | | `pattern` | string | Yes | A PCRE regex pattern (including delimiters, e.g. `/foo/i`). | | `replacement` | string | Yes | Replacement string (supports backreferences like `$1`). | | `limit` | int | No | Max replacements. Default `-1` (all). | ``` [[ post.post_title | regex_replace('/\\s+/', '-') ]] ``` **Common use case — strip Yoast/plugin-inserted footer text:** ``` [[ post.post_content | regex_replace('/The post .* (?:appeared first|first appeared) .*\./', '') ]] ``` *** #### `intl_date` Formats a `DateTime` object using the ICU pattern format via PHP's `IntlDateFormatter`. Useful for localized date strings. | Argument | Type | Default | Description | | --------- | ------ | ----------------------------- | ----------------------------------------------- | | `locale` | string | `es_ES` | A BCP 47 locale string (e.g. `en_US`, `fr_FR`). | | `pattern` | string | `EEEE d, 'de' MMMM 'de' yyyy` | ICU date pattern. | ``` [[ feedotter.send_date_object | intl_date('en_US', 'MMMM d, yyyy') ]] [[ feedotter.send_date_object | intl_date ]] ``` *** #### `switch_timezone` Converts a `DateTime` object to a different timezone and returns the adjusted `DateTime`. Typically chained before a `date` format filter. | Argument | Type | Description | | ---------- | ------ | --------------------------------------------------------- | | `timezone` | string | A valid PHP timezone identifier (e.g. `America/Chicago`). | ``` [[ feedotter.send_date_object | switch_timezone('America/New_York') | date('F j, Y') ]] ``` *** #### `splitsentences` Splits a block of text into an array of individual sentences. Sentences shorter than 4 characters are discarded. Typically used with a `[% for %]` loop. ``` [% for sentence in post.post_content | splitsentences %]

[[ sentence ]]

[% endfor %] ``` *** #### `shuffle` Randomly shuffles an array of posts or items. Each render produces a different order. ``` [% set posts = posts | shuffle %] ``` *** #### `marker` Tags an array of posts with a named marker (recording their URLs internally) and returns the array unchanged. Used by FeedOtter for deduplication tracking. | Argument | Type | Description | | ------------ | ------ | ------------------------------------------- | | `markerName` | string | An arbitrary label for this group of posts. | ``` [% set featured = posts | marker('featured') %] ``` *** #### `kebab` Converts a string to lowercase kebab-case, stripping non-alphanumeric characters and replacing spaces with hyphens. ``` [[ post.post_title | kebab ]] [[ "My Article Title" | kebab ]] {# → my-article-title #} ``` *** ### Commonly Used Built-in Filters These standard Twig filters are also available in FeedOtter templates. | Filter | Description | Example | | --------------------------------------- | -------------------------------------------------- | ------------------------------------------------------------ | | `date(format)` | Format a date/DateTime. | `[[ feedotter.send_date_object \| date('F Y') ]]` | | `truncate(length, preserve, separator)` | Truncate plain text. | `[[ post.post_excerpt_text \| truncate(200, true, '...') ]]` | | `upper` | Uppercase a string. | `[[ post.post_title \| upper ]]` | | `lower` | Lowercase a string. | `[[ post.post_title \| lower ]]` | | `capitalize` | Capitalize the first character. | `[[ post.post_title \| capitalize ]]` | | `title` | Title-case every word. | `[[ post.post_title \| title ]]` | | `trim` | Strip leading/trailing whitespace. | `[[ custom.field \| trim ]]` | | `nl2br` | Convert newlines to `
` tags. | `[[ custom.bio \| nl2br ]]` | | `replace({'old':'new'})` | Find-and-replace within a string. | `[[ post.post_title \| replace({'&': 'and'}) ]]` | | `default(fallback)` | Return a fallback if the value is empty. | `[[ custom.headline \| default('Read More') ]]` | | `length` | Count characters in a string or items in an array. | `[% if post.post_title \| length > 60 %]` | | `slice(start, length)` | Return a portion of a string or array. | `[[ posts \| slice(0, 3) ]]` | | `join(glue)` | Join an array into a string. | `[[ tags \| join(', ') ]]` | | `first` | First item of an array. | `[[ posts \| first ]]` | | `last` | Last item of an array. | `[[ posts \| last ]]` | | `reverse` | Reverse a string or array. | `[[ posts \| reverse ]]` | | `sort` | Sort an array. | `[[ tags \| sort ]]` | | `url_encode` | URL-encode a string. | `[[ post.post_url \| url_encode ]]` | | `json_encode` | Encode a value as JSON. | `[[ data \| json_encode ]]` | #### `striptags` Strips HTML tags from a string. When called with no argument, all tags are removed. Pass an allowlist of tags to keep specific ones — useful when you need to render CMS HTML in email without carrying over layout-heavy or unknown markup. ``` {{-- Remove all tags (plain text only) --}} [[ post.post_content | striptags ]] {{-- Keep only email-safe inline/block tags --}} [[ post.post_content | striptags('


') ]] ``` > **Note:** Even with an allowlist, CMS content can still carry unsafe `style` attributes or deeply nested structures. Pair with `cleanImages` and `regex_replace` to further sanitize. **Full cleanup chain for CMS HTML content:** ``` [[ post.post_content | regex_replace('/The post .* (?:appeared first|first appeared) .*\./', '') | striptags('


') | cleanImages ]] ``` *** ### Rarely Used / Specialist Filters These filters are available but not commonly needed in standard templates. #### `truncate_html` Truncates an HTML string to approximately `length` plain-text characters, preferring a sentence boundary, then a word boundary. Automatically closes any tags left open by the cut. | Argument | Type | Default | Description | | -------- | ---- | ------- | ---------------------------------------- | | `length` | int | `100` | Maximum number of plain-text characters. | ``` [[ post.post_content | truncate_html(300) ]] ``` *** #### `truncate_sentence` Truncates a **plain-text** string to `length` characters, snapping back to the nearest sentence-ending punctuation (`.`, `?`, or `!`) so the result never ends mid-sentence. | Argument | Type | Description | | -------- | ---- | --------------------------------------------------------------- | | `length` | int | Maximum character count before snapping to a sentence boundary. | ``` [[ post.post_excerpt_text | truncate_sentence(200) ]] ``` *** #### `resize2` Alternative resize filter backed by Cloudinary. Resizes to the given width (and optional height) using a fill crop. Returns a Cloudinary fetch URL. | Argument | Type | Required | Description | | -------- | ---- | -------- | ------------------------ | | `width` | int | Yes | Target width in pixels. | | `height` | int | No | Target height in pixels. | ``` [[ post.image_url | resize2(600, 400) ]] ``` *** #### `mktohash` Generates a random alphanumeric string of a given length. Useful for Marketo hash tokens or unique identifiers. | Argument | Type | Default | Description | | -------- | ---- | ------- | --------------------------------- | | `length` | int | `12` | Number of characters to generate. | ``` [[ 'seed' | mktohash(16) ]] ``` *** #### `foDebugJson` Pretty-prints any value (object, array, or scalar) as an HTML-escaped JSON string. Intended for template debugging only — remove before sending. ``` [[ post | foDebugJson ]] ``` *** *Last updated: August 2026*