Add, Delete & Rename Keys with jq

Editing keys in place — without rebuilding the whole object by hand.

Example input

{ "id": 7, "fname": "Ada", "temp": "x", "age": 36 }

Add or update a field

jq '.country = "UK"' data.json          # add/overwrite .country
jq '.age += 1' data.json                # update in place
jq '. + { active: true }' data.json     # merge in extra fields

Delete a key

jq 'del(.temp)' data.json

Delete several keys at once

jq 'del(.temp, .id)' data.json

Delete a key from every object in an array

jq 'map(del(.temp))' people.json

Rename one key

Copy to the new name, then delete the old:

jq '.firstName = .fname | del(.fname)' data.json

Output:

{ "id": 7, "temp": "x", "age": 36, "firstName": "Ada" }

Rename keys by pattern (with_entries)

with_entries exposes each {key, value} so you can rewrite keys — e.g. strip a prefix or camelCase them:

jq 'with_entries(.key |= sub("^f"; "first_"))' data.json

Uppercase every key:

jq 'with_entries(.key |= ascii_upcase)' data.json

|= updates in place: .age |= . + 1 reads, transforms, and writes the same path. For renames, with_entries(...) (sugar over to_entries | map(...) | from_entries) is the clean way to rewrite many keys at once.