jq Online Playground

jq Filter Reference

The most commonly used jq expressions, with examples you can click to load directly into the playground.

Identity & Field Access

Filter	Description	Example output
.	Identity — returns the input unchanged	The full input
.key	Extract a field from an object	.name → "Alice"
.key.nested	Access nested fields	.user.address.city
.["key"]	Access fields with special characters	.["first-name"]
.key?	Extract field, return null if missing (no error)	.missing? → null

Arrays

Filter	Description	Example
.[]	Iterate all elements of an array or object	Streams each element
.[0]	Get element by index (negative counts from end)	.[-1] → last item
.[2:5]	Slice from index 2 to 4	Returns 3 elements
length	Number of elements in array, characters in string	[1,2,3] | length → 3
first	First element of an array	Same as .[0]
last	Last element of an array	Same as .[-1]
reverse	Reverse the order of an array	[3,1,2] | reverse → [2,1,3]
unique	Remove duplicate values	[1,2,1] | unique → [1,2]
flatten	Flatten nested arrays	[[1,[2]],3] | flatten → [1,2,3]
min / max	Minimum or maximum value in an array	[3,1,2] | max → 3
min_by(.f) / max_by(.f)	Min/max by a field	min_by(.age)
add	Sum numbers, concatenate strings or arrays	[1,2,3] | add → 6
indices("x")	All indices where value appears	"abab" | indices("a") → [0,2]

Transformation

Filter	Description	Example
map(f)	Apply filter to each element, return array	map(.name) → ["Alice","Bob"]
map_values(f)	Apply filter to each value in object	map_values(. * 2)
select(cond)	Keep elements where condition is true	.[] | select(.age > 18)
sort	Sort a simple array	[3,1,2] | sort → [1,2,3]
sort_by(.f)	Sort array of objects by a field	sort_by(.name)
group_by(.f)	Group elements by a field value	group_by(.role)
unique_by(.f)	Remove duplicates by field	unique_by(.id)
to_entries	Convert object to [{key, value}] array	{"a":1} | to_entries
from_entries	Convert [{key, value}] back to object	Inverse of to_entries
with_entries(f)	to_entries | map(f) | from_entries	Transform key/value pairs
keys	Get array of object keys, sorted	{"b":2,"a":1} | keys → ["a","b"]
values	Get array of object values	{"a":1} | values → [1]
has("key")	Test if object has a key	has("name") → true/false
in(obj)	Test if value is a key in obj	"name" | in({"name":1})
contains(x)	Test if input contains x	[1,2,3] | contains([2])

Pipes & Composition

Filter	Description	Example
f | g	Pipe output of f into g	.users | map(.name)
f, g	Produce outputs from both f and g	.a, .b
[f]	Collect all outputs of f into an array	[.[] | .name]
{a: .x, b: .y}	Construct a new object	{name: .name, age: .age}
empty	Produce no output (useful with select)	Filters out values
not	Boolean negation	select(.active | not)
type	Get the type of a value	"hello" | type → "string"
tostring	Convert value to a JSON string	42 | tostring → "42"
tonumber	Convert string to number	"42" | tonumber → 42
ascii_downcase	Lowercase a string	"HELLO" | ascii_downcase
ascii_upcase	Uppercase a string	"hello" | ascii_upcase
ltrimstr("x") / rtrimstr("x")	Remove prefix / suffix from string	"foobar" | ltrimstr("foo") → "bar"
split("x") / join("x")	Split string / join array into string	"a,b" | split(",") → ["a","b"]
test("regex")	Test if string matches regex	"foo" | test("f.*") → true

Common jq Recipes

Extract a field from every object in an array

Given a JSON array of users, get all names:

[.[] | .name]
# or equivalently:
map(.name)

Filter an array by condition

Keep only active admins:

.[] | select(.active == true and .role == "admin")

Reshape objects

Create a new object with only the fields you need:

map({ id: .id, fullName: .name, isAdmin: (.role == "admin") })

Sort and deduplicate

# Sort by age, oldest first
sort_by(.age) | reverse

# Remove duplicates by email
unique_by(.email)

Group and count

# Group users by role, count each group
group_by(.role) | map({ role: .[0].role, count: length })

Extract nested values safely

# Returns null instead of error if path is missing
.user?.address?.city?

Frequently Asked Questions

Need to lint or fix your JSON first?

If your JSON has syntax errors — trailing commas, single quotes, comments, missing brackets — use the JSON Linter and Fixer to repair it before filtering.