Ansible Jinja2 Filters: Transform Data in Playbooks (Complete Reference)

Jinja2 filters transform data inline within Ansible playbooks. They convert types, format strings, filter lists, parse JSON/YAML, manipulate IPs, and more — all using the pipe (|) syntax.

String Filters

vars:
  name: "ansible automation"
tasks:
  - ansible.builtin.debug:
      msg:
        upper: "{{ name | upper }}"                    # ANSIBLE AUTOMATION
        lower: "{{ name | lower }}"                    # ansible automation
        title: "{{ name | title }}"                    # Ansible Automation
        capitalize: "{{ name | capitalize }}"          # Ansible automation
        replace: "{{ name | replace('ansible', 'red hat') }}"  # red hat automation
        trim: "{{ '  hello  ' | trim }}"               # hello
        length: "{{ name | length }}"                  # 20
        truncate: "{{ name | truncate(10) }}"          # ansible...
        regex_replace: "{{ name | regex_replace('auto.*', 'platform') }}"  # ansible platform
        regex_search: "{{ name | regex_search('auto\\w+') }}"             # automation
        split: "{{ name | split(' ') }}"               # ['ansible', 'automation']
        join: "{{ ['a', 'b', 'c'] | join(', ') }}"    # a, b, c

See also: Ansible default() Filter: Set Fallback Values for Undefined Variables

List Filters

vars:
  servers: [web1, db1, web2, db2, web1]
  numbers: [3, 1, 4, 1, 5, 9, 2, 6]
tasks:
  - ansible.builtin.debug:
      msg:
        unique: "{{ servers | unique }}"              # [web1, db1, web2, db2]
        sort: "{{ numbers | sort }}"                  # [1, 1, 2, 3, 4, 5, 6, 9]
        reverse: "{{ numbers | reverse | list }}"     # [6, 2, 9, 5, 1, 4, 1, 3]
        first: "{{ servers | first }}"                # web1
        last: "{{ servers | last }}"                  # web1
        length: "{{ servers | length }}"              # 5
        flatten: "{{ [[1,2],[3,4]] | flatten }}"      # [1, 2, 3, 4]
        min: "{{ numbers | min }}"                    # 1
        max: "{{ numbers | max }}"                    # 9
        sum: "{{ numbers | sum }}"                    # 31
        random: "{{ servers | random }}"              # random element
        shuffle: "{{ servers | shuffle }}"            # random order
        difference: "{{ [1,2,3,4] | difference([2,4]) }}"  # [1, 3]
        intersect: "{{ [1,2,3] | intersect([2,3,4]) }}"    # [2, 3]
        union: "{{ [1,2] | union([2,3]) }}"           # [1, 2, 3]

Select & Reject Filters

vars:
  users:
    - name: alice
      role: admin
      active: true
    - name: bob
      role: developer
      active: false
    - name: charlie
      role: admin
      active: true
tasks:
  # Filter by attribute
  - name: Get active users
    ansible.builtin.debug:
      msg: "{{ users | selectattr('active') | list }}"
- name: Get admins
    ansible.builtin.debug:
      msg: "{{ users | selectattr('role', 'equalto', 'admin') | list }}"
- name: Get admin names only
    ansible.builtin.debug:
      msg: "{{ users | selectattr('role', 'eq', 'admin') | map(attribute='name') | list }}"
    # ['alice', 'charlie']
- name: Get inactive users
    ansible.builtin.debug:
      msg: "{{ users | rejectattr('active') | list }}"
# Filter simple lists
  - name: Numbers greater than 3
    ansible.builtin.debug:
      msg: "{{ [1,2,3,4,5] | select('greaterthan', 3) | list }}"
    # [4, 5]
- name: Strings matching pattern
    ansible.builtin.debug:
      msg: "{{ ['web1','db1','web2','cache1'] | select('match', 'web.*') | list }}"
    # ['web1', 'web2']

See also: Ansible map Filter: Extract Attributes from Lists (Complete Guide)

Dictionary Filters

vars:
  config:
    host: db.example.com
    port: 5432
    name: myapp
    password: secret
tasks:
  - ansible.builtin.debug:
      msg:
        keys: "{{ config | dict2items | map(attribute='key') | list }}"
        items: "{{ config | dict2items }}"
        combine: "{{ config | combine({'port': 3306, 'ssl': true}) }}"

dict2items / items2dict

# Convert dict → list of {key, value}
- name: Iterate dictionary
  ansible.builtin.debug:
    msg: "{{ item.key }} = {{ item.value }}"
  loop: "{{ config | dict2items }}"
# Convert list → dict
- name: Build dict from list
  ansible.builtin.set_fact:
    rebuilt: "{{ [{'key': 'a', 'value': 1}, {'key': 'b', 'value': 2}] | items2dict }}"
  # {a: 1, b: 2}

Type Conversion

- ansible.builtin.debug:
    msg:
      to_int: "{{ '42' | int }}"                # 42
      to_float: "{{ '3.14' | float }}"           # 3.14
      to_bool: "{{ 'true' | bool }}"             # true
      to_json: "{{ config | to_json }}"           # JSON string
      to_yaml: "{{ config | to_yaml }}"           # YAML string
      to_nice_json: "{{ config | to_nice_json }}" # Pretty JSON
      from_json: "{{ json_string | from_json }}"  # Parse JSON
      from_yaml: "{{ yaml_string | from_yaml }}"  # Parse YAML
      string: "{{ 42 | string }}"                 # "42"

See also: Ansible regex_replace Filter: Find & Replace with Regex (Complete Guide)

Default Values

# Set default if undefined
- ansible.builtin.debug:
    msg: "{{ optional_var | default('fallback') }}"
# Default with boolean check (empty string/list/0 → default)
- ansible.builtin.debug:
    msg: "{{ maybe_empty | default('fallback', true) }}"
# Chained defaults
- ansible.builtin.debug:
    msg: "{{ primary | default(secondary) | default('last_resort') }}"
# Mandatory — fail if undefined
- ansible.builtin.debug:
    msg: "{{ required_var | mandatory }}"

JSON Query (json_query)

vars:
  instances:
    - name: web1
      ip: 10.0.0.1
      tags: {env: prod, role: web}
    - name: db1
      ip: 10.0.0.2
      tags: {env: prod, role: db}
    - name: web-dev
      ip: 10.0.1.1
      tags: {env: dev, role: web}
tasks:
  - name: Get all IPs
    ansible.builtin.debug:
      msg: "{{ instances | json_query('[*].ip') }}"
    # [10.0.0.1, 10.0.0.2, 10.0.1.1]
- name: Get prod instances
    ansible.builtin.debug:
      msg: "{{ instances | json_query('[?tags.env==`prod`].name') }}"
    # [web1, db1]
- name: Get web server IPs
    ansible.builtin.debug:
      msg: "{{ instances | json_query('[?tags.role==`web`].ip') }}"
    # [10.0.0.1, 10.0.1.1]

IP Address Filters

- ansible.builtin.debug:
    msg:
      network: "{{ '192.168.1.5/24' | ipaddr('network') }}"      # 192.168.1.0
      netmask: "{{ '192.168.1.5/24' | ipaddr('netmask') }}"      # 255.255.255.0
      broadcast: "{{ '192.168.1.5/24' | ipaddr('broadcast') }}"   # 192.168.1.255
      address: "{{ '192.168.1.5/24' | ipaddr('address') }}"       # 192.168.1.5
      prefix: "{{ '192.168.1.5/24' | ipaddr('prefix') }}"         # 24
      is_ipv4: "{{ '192.168.1.1' | ansible.utils.ipv4 }}"         # 192.168.1.1
      is_ipv6: "{{ '::1' | ansible.utils.ipv6 }}"                 # ::1

Hash and Encryption

- ansible.builtin.debug:
    msg:
      sha256: "{{ 'hello' | hash('sha256') }}"
      md5: "{{ 'hello' | hash('md5') }}"
      password: "{{ 'mypassword' | password_hash('sha512') }}"
      b64encode: "{{ 'hello world' | b64encode }}"
      b64decode: "{{ 'aGVsbG8gd29ybGQ=' | b64decode }}"

Path Filters

- ansible.builtin.debug:
    msg:
      basename: "{{ '/etc/nginx/nginx.conf' | basename }}"    # nginx.conf
      dirname: "{{ '/etc/nginx/nginx.conf' | dirname }}"      # /etc/nginx
      expanduser: "{{ '~/docs' | expanduser }}"                # /home/user/docs
      realpath: "{{ '/etc/nginx/../hosts' | realpath }}"       # /etc/hosts
      splitext: "{{ 'file.tar.gz' | splitext }}"               # ('file.tar', '.gz')

Ternary (Conditional)

- ansible.builtin.debug:
    msg: "{{ (ansible_os_family == 'Debian') | ternary('apt', 'yum') }}"
- name: Set package manager
  ansible.builtin.set_fact:
    pkg_mgr: "{{ (ansible_os_family == 'RedHat') | ternary('dnf', 'apt') }}"

FAQ

What are Ansible Jinja2 filters?

Filters transform data using the pipe (|) syntax in Ansible templates and playbooks. They convert types, format strings, filter lists, parse JSON/YAML, and more — executed inline without separate tasks.

What is the difference between select and selectattr?

select filters simple lists by value ([1,2,3] | select('greaterthan', 1)). selectattr filters lists of dictionaries by attribute (users | selectattr('active', 'equalto', true)).

How do I set a default value for undefined variables?

Use the default filter: {{ my_var | default('fallback') }}. Add true as second argument to also trigger default on empty values: {{ my_var | default('fallback', true) }}.

How do I parse JSON in Ansible?

Use from_json: {{ json_string | from_json }}. For querying complex JSON structures, use json_query with JMESPath expressions: {{ data | json_query('[?status==active].name') }}.

Conclusion

Most-used filters quick reference: • default() — Fallback for undefined variables • selectattr() / map() — Filter and transform lists of dicts • to_json / from_json — Serialize/parse JSON • regex_replace() / regex_search() — Pattern matching • combine() — Merge dictionaries • json_query() — JMESPath queries on complex data

Related Articles

• Ansible map Filter: Transform Lists • Ansible regex_replace: Search & Replace • Ansible default() Filter: Set Fallback Values • Ansible Variable Precedence Guide • Ansible regex_search Filter Guide • Can You Use assert in Jinja Templates? • Ansible Compare Lists: difference, intersect, union