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Filters

Filters transform data in expressions using Liquid — a templating language standard. Each filter takes an input value, applies a transformation, and outputs a new value.

Filters are chained in expressions. Example: posts → first → title → upcase uses three filters (first, title is a navigation property, upcase is a filter).

This page documents every available filter with its input/output type, options, and examples.

String filters

These filters work on text values.

strip_html

Removes all HTML tags from a string.

Input: String (e.g., <p>Hello <strong>world</strong></p>) Output: String (e.g., Hello world) Options: None Example: post_content → strip_html removes HTML from rich text fields

append

Adds text to the end of a string.

Input: String Output: String Options: value (text to append) Example: post_title → append(" - Blog") changes "My Post" to "My Post - Blog"

prepend

Adds text to the beginning of a string.

Input: String Output: String Options: value (text to prepend) Example: post_title → prepend("New: ") changes "My Post" to "New: My Post"

upcase

Converts a string to uppercase.

Input: String Output: String Options: None Example: post_title → upcase changes "hello" to "HELLO"

downcase

Converts a string to lowercase.

Input: String Output: String Options: None Example: post_title → downcase changes "Hello" to "hello"

capitalize

Capitalizes the first character and lowercases the rest.

Input: String Output: String Options: None Example: "hello WORLD" → capitalize becomes "Hello world"

replace

Replaces all occurrences of a substring with another.

Input: String Output: String Options: search (text to find), replace (replacement text) Example: "Hello World" → replace("World", "Silex") becomes "Hello Silex"

replace_first

Replaces only the first occurrence of a substring.

Input: String Output: String Options: search, replace Example: "aaa" → replace_first("a", "b") becomes "baa"

replace_last

Replaces only the last occurrence of a substring.

Input: String Output: String Options: search, replace Example: "aaa" → replace_last("a", "b") becomes "aab"

remove

Removes all occurrences of a substring (equivalent to replace with empty string).

Input: String Output: String Options: search (text to remove) Example: "Hello World" → remove("World") becomes "Hello "

remove_first

Removes only the first occurrence of a substring.

Input: String Output: String Options: search Example: "aaa" → remove_first("a") becomes "aa"

remove_last

Removes only the last occurrence of a substring.

Input: String Output: String Options: search Example: "aaa" → remove_last("a") becomes "aa"

truncate

Shortens a string to a maximum length.

Input: String Output: String Options: length (max characters, default 50) Example: "This is a very long sentence" → truncate(10) becomes "This is a "

truncatewords

Shortens a string to a maximum number of words.

Input: String Output: String Options: length (max words, default 15) Example: "This is a very long sentence" → truncatewords(3) becomes "This is a"

escape

Escapes double quotes in a string.

Input: String Output: String Options: None Example: post_title → escape converts "Hello" to \"Hello\"

escape_once

Escapes double quotes (once, even if already escaped).

Input: String Output: String Options: None

newline_to_br

Converts newlines (\n) to HTML break tags (<br />).

Input: String Output: String Options: None Example: "Line 1\nLine 2" → newline_to_br becomes "Line 1<br />Line 2"

strip_newlines

Removes all newlines from a string.

Input: String Output: String Options: None Example: "Line 1\nLine 2" → strip_newlines becomes "Line 1Line 2"

Array filters

These filters work on lists.

where

Filters a list to items matching a condition.

Input: List of objects Output: List of objects Options: key (field name), value (value to match) Example: posts → where(category = "news") returns only posts in the news category

find

Returns the first item in a list matching a condition.

Input: List of objects Output: One object Options: key, value Example: posts → find(id = 5) returns the post with id 5

first

Returns the first item in a list.

Input: List Output: One item Options: None Example: posts → first returns the first post

last

Returns the last item in a list.

Input: List Output: One item Options: None Example: posts → last returns the last post

join

Joins a list of strings into a single string with a separator.

Input: List of strings Output: String Options: separator (what to put between items, default ",") Example: tags → join(", ") joins tags with commas: "tag1, tag2, tag3"

split

Splits a string into a list using a separator.

Input: String Output: List of strings Options: separator (what to split on, default ",") Example: "tag1, tag2, tag3" → split(", ") becomes a list of three tags

map

Extracts a specific field from each item in a list.

Input: List of objects Output: List of values Options: key (field name to extract) Example: posts → map(title) extracts all post titles into a list

reverse

Reverses the order of a list.

Input: List Output: List (reversed) Options: None Example: posts → reverse returns posts in reverse order

size

Returns the number of items in a list (or characters in a string).

Input: List or String Output: Number Options: None Example: posts → size returns the count of posts

slice

Extracts a portion of a list by start and end index.

Input: List Output: List Options: start (start index), end (end index) Example: posts → slice(0, 3) returns the first 3 items

sort

Sorts a list of objects by a field name (alphabetically or numerically).

Input: List of objects Output: List (sorted) Options: key (field to sort by) Example: posts → sort(title) sorts posts alphabetically by title

compact

Removes empty/null/false items from a list.

Input: List Output: List (without empty values) Options: None Example: authors → compact removes null author entries

sample

Picks one or more random items from a list.

Input: List Output: List or single item Options: count (number of items to pick, default 1) Example: posts → sample(3) returns 3 random posts

Math filters

These filters work on numbers.

plus

Adds a number to another number.

Input: Number Output: Number Options: value (number to add) Example: price → plus(10) adds $10 to the price

minus

Subtracts a number.

Input: Number Output: Number Options: value (number to subtract) Example: price → minus(5) subtracts $5 from the price

times

Multiplies a number.

Input: Number Output: Number Options: value (number to multiply by) Example: quantity → times(2) doubles the quantity

divided_by

Divides a number.

Input: Number Output: Number Options: value (number to divide by) Example: total → divided_by(2) divides the total by 2

modulo

Returns the remainder after division.

Input: Number Output: Number Options: value (divisor) Example: count → modulo(2) returns 0 if even, 1 if odd

ceil

Rounds up to the nearest integer.

Input: Number Output: Integer Options: None Example: 3.2 → ceil becomes 4

floor

Rounds down to the nearest integer.

Input: Number Output: Integer Options: None Example: 3.8 → floor becomes 3

round

Rounds to the nearest integer.

Input: Number Output: Integer Options: None Example: 3.5 → round becomes 4

abs

Returns the absolute (positive) value.

Input: Number Output: Number Options: None Example: -5 → abs becomes 5

at_least

Returns the larger of the number or a minimum value.

Input: Number Output: Number Options: value (minimum) Example: price → at_least(10) ensures price is at least 10

at_most

Returns the smaller of the number or a maximum value.

Input: Number Output: Number Options: value (maximum) Example: discount → at_most(50) ensures discount doesn't exceed 50

Date filters

date

Formats a date string using a format string.

Input: String (date in ISO format, e.g., "2025-03-27") Output: String (formatted, e.g., "Mar 27, 25") Options: format (format string using % codes), timeZone (IANA timezone, default "UTC")

Format codes: - %Y — 4-digit year (2025) - %y — 2-digit year (25) - %m — 2-digit month (03) - %d — 2-digit day (27) - %b — short month name (Mar) - %a — short weekday name (Thu) - %H — 2-digit hour (14) - %M — 2-digit minute (30) - %S — 2-digit second (45)

Example: post_date → date("%a, %b %d, %Y") formats "2025-03-27" as "Thu, Mar 27, 2025"

Timezones: Use standard IANA timezone names: UTC, Europe/Paris, America/New_York, Asia/Tokyo, etc.

Filter combinations

You can chain filters together to combine transformations.

Example 1: List of formatted post dates 

posts → map(publish_date) → first → date("%Y-%m-%d")
Gets all posts, extracts publish dates, takes the first, and formats it.

Example 2: Post excerpt without HTML 

post_content → truncate(200) → strip_html
Shortens the content to 200 characters and removes HTML tags.

Example 3: Count of published posts 

posts → where(status = "published") → size
Filters to published posts and counts them.

Common mistakes

  • Using a filter on the wrong data type. upcase only works on strings. Silex will prevent this in the editor.
  • Forgetting filter options. Some filters require options (where needs key and value). The editor will prompt you.
  • Chaining incompatible filters. If a filter outputs a number, the next filter must accept a number. Pay attention to input/output types.
  • Not escaping special characters in options. If your where value contains quotes, make sure it's properly quoted.

Learn more

Quiz

Q1: You want to extract the first 3 words from a post title. Which filter do you use?

  • A) truncate
  • B) truncatewords
  • C) slice
Answer

B) truncatewords — truncatewords limits a string to a number of words. truncate limits characters. slice works on arrays.

Q2: You have a list of posts and want to get only those published in the "news" category. What filter do you use?

  • A) find
  • B) where
  • C) slice
Answer

B) where — where filters a list by a condition. find returns the first match. slice extracts a range by index.

Q3: You want to add "$" to the beginning of a price. Which filter(s) do you chain?

  • A) prepend("$")
  • B) plus("$")
  • C) append("$")
Answer

A) prepend("$") — prepend adds to the beginning. append adds to the end. plus is for adding numbers.

Q4: You want to show the count of blog posts. What expression returns a number?

  • A) posts
  • B) posts → size
  • C) posts → count
Answer

B) posts → size — size returns the count of items in a list. posts alone returns the list itself, not a count.

Q5: You have a date "2025-03-27" and want to display it as "27/03/2025". What date format string do you use?

  • A) %d/%m/%Y
  • B) %Y/%m/%d
  • C) %d-%m-%Y
Answer

A) %d/%m/%Y — %d is day, %m is month, %Y is 4-digit year. This outputs day/month/year.

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