---
title: Filter collections before entering loops
description: >-
Pre-filter collections using Liquid filters before loops to reduce
per-iteration conditional overhead that multiplies across all iterations and
increases TTFB.
source_url:
html: >-
https://shopify.dev/docs/storefronts/themes/best-practices/performance/avoid-conditionals-in-loops
md: >-
https://shopify.dev/docs/storefronts/themes/best-practices/performance/avoid-conditionals-in-loops.md
api_name: liquid
---
# Filter collections before entering loops
Pre-filter collections using Liquid filters before loops. Move complex conditional logic outside of [`for`](https://shopify.dev/docs/api/liquid/tags/for) loops to reduce processing overhead that multiplies across iterations.
***
## Why
Conditional checks have a processing cost. When placed inside a [`for`](https://shopify.dev/docs/api/liquid/tags/for) loop, the number of iterations multiplies this cost. A collection with 50 products and 3 conditional checks per iteration means 150 conditional evaluations. If you can pre-filter the collection down to 12 matching products before entering the loop, then you evaluate 12 iterations with 1 conditional each: 12 evaluations instead of 150.
Complex conditions with multiple `and`/`or` operators are more expensive because each operator requires a separate evaluation. This processing adds directly to server-side Liquid rendering time, increasing TTFB, which in turn delays FCP and LCP.
***
## How
Use Liquid filters to narrow the collection before the loop starts:
* [`where`](https://shopify.dev/docs/api/liquid/filters/where): Filters objects by a property value. `collection.products | where: "available"` returns only available products.
* [`map`](https://shopify.dev/docs/api/liquid/filters/map): Extracts a single property from each object. Useful for building arrays to check against.
* [`sort`](https://shopify.dev/docs/api/liquid/filters/sort): Sorts objects by a property. Sort once before the loop rather than sorting within the loop.
* [`compact`](https://shopify.dev/docs/api/liquid/filters/compact): Removes `nil` values from an array after mapping or filtering.
* [`uniq`](https://shopify.dev/docs/api/liquid/filters/uniq): Removes duplicates from an array.
You can chain multiple filters together to apply several conditions before the loop:
```liquid
{% assign filtered = collection.products | where: "available" | sort: "price" %}
```
For conditions that can't be expressed as `where` filters, such as price ranges, tag checks, and compound logic, pre-compute a lookup variable before the loop to simplify the in-loop check.
***
## Examples
### Basic pre-filtering with `where`
Less performant:
```liquid
{%- for product in collection.products -%}
{% if product.available %}
{{ product.title }} - {{ product.price | money }}
{% endif %}
{%- endfor -%}
```
More performant:
```liquid
{% assign available_products = collection.products | where: "available" %}
{%- for product in available_products -%}
{{ product.title }} - {{ product.price | money }}
{%- endfor -%}
```
### Compound filtering: available, tagged, and within a price range
When you need multiple conditions, apply as many as possible before the loop using filters, then handle the remaining conditions with a single in-loop check:
```liquid
{%- comment -%}
Pre-filter: available products only.
The where filter handles the boolean check outside the loop.
{%- endcomment -%}
{% assign candidates = collection.products | where: "available" %}
{%- comment -%}
In-loop: check tag and price range.
These conditions can't be expressed with the where filter,
but the loop now iterates over fewer products.
{%- endcomment -%}
{%- for product in candidates -%}
{% if product.tags contains 'featured' and product.price >= 1000 and product.price <= 5000 %}
{{ product.featured_image | image_url: width: 400 | image_tag: loading: 'lazy' }}
{{ product.title }}
{{ product.price | money }}
{{ product.featured_image | image_url: width: 400 | image_tag: loading: 'lazy' }}
{{ product.title }}
{% else %}
{{ product.featured_image | image_url: width: 400 | image_tag: loading: 'lazy' }}
{{ product.title }}
{% endif %}
{%- endfor -%}
```
### Chaining multiple filters
Combine `where`, `sort`, and other filters to build the exact dataset before iterating:
```liquid
{%- comment -%}
Get available products, sort by price ascending.
The loop body has no conditionals at all.
{%- endcomment -%}
{% assign sorted_available = collection.products | where: "available" | sort: "price" %}
{%- for product in sorted_available -%}
{{ product.featured_image | image_url: width: 400 | image_tag: loading: 'lazy' }}
{{ product.title }}
{{ product.price | money }}