Access Fields & Nested Keys with jq (.a.b.c)

Getting one value out is the most common jq task. Chain keys with dots and index arrays with [n].

Example input

{
  "user": { "name": "Ada", "roles": ["admin", "dev"] },
  "active": true
}

Top-level and nested keys

jq '.active' data.json        # true
jq '.user.name' data.json     # "Ada"

Array elements

jq '.user.roles[0]' data.json   # "admin"
jq '.user.roles[-1]' data.json  # "dev"  (negative = from the end)

Keys with spaces or special characters

Quote them:

jq '.["first name"]' data.json

Avoid “Cannot index null with …” on missing keys

Indexing into a missing/null path errors. Add ? to make it return null (or nothing) instead:

jq '.user.address.city?' data.json     # no error if address is missing

Provide a fallback with the alternative operator //:

jq '.user.nickname // "anonymous"' data.json

Get the keys of an object

jq 'keys' data.json            # ["active","user"]  (sorted)
jq 'keys_unsorted' data.json   # original order

? vs //: ? suppresses the error from a bad path; // supplies a value when the left side is null or false. Combine them — .a.b? // "default" — for “safe access with a fallback”.