jq Playground — test jq expressions online.

It is real jq. The page loads jq 1.8.2 compiled to WebAssembly — the actual C program, 907 KB uncompressed and 250–340 KB over the wire depending on whether your browser negotiates brotli or gzip — and runs your filter through it. The version badge next to the flags is read out of that binary at runtime, not written into the page, so it cannot drift. Nothing here approximates jq's behaviour, because nothing here reimplements it: the same code that runs on your laptop runs in your tab.

No. There is no server, no API and no logging. jq is fetched once from this site as a static asset and then executes entirely inside your tab, which is the difference between this and a server-side playground: with jqplay.org and friends, the JSON you paste is sent to someone else's machine to be evaluated. You can safely paste production kubectl output, API responses with tokens in them, and logs with customer data.

Four toggles: -r (raw string output), -s (slurp the input stream into one array), -n (run once with null input) and -c (compact, one line per result). Not exposed in this version: --arg and --argjson, module loading (-L, include, import — jq answers "module not found"), --seq, colour output, file arguments and reading from a URL. You can replace --arg inside the program itself: ("prod") as $ns | … binds a value the same way.

Usually because a builtin it used does not exist in jq 1.8.2. leaf_paths is the classic one — it was removed, and jq now answers "leaf_paths/0 is not defined"; the working spelling is paths(scalars). The same happens with invented flags and with builtins from other tools (jaq, gojq, JMESPath) that never existed in jq. A compile error here quotes jq's own message, line, column and caret, so you can see exactly which token it rejected rather than guessing.

-s reads every value in the input stream into one array and runs your filter once on that array: 1 2 3 becomes [1,2,3]. -n runs the filter once with null as input and hands you the stream through the inputs generator, so [inputs] on 1 2 3 also gives [1,2,3] — but you control when each value is pulled, which is what lets you pair values, skip a header record, or stop early. -s buffers everything first; -n plus inputs streams.

Because -r only removes the quotes around string results. Anything that is not a string — an object, array, number, boolean or null — is still printed as JSON, which is why . on {"a":1} looks identical with and without -r. If you want text out of a non-string, convert it in the filter: tostring, @csv, @tsv, join(","), or an interpolated string like "\(.name) → \(.image)".

Build an array per row and pipe it through @csv or @tsv, then turn on -r so the row is printed as text rather than as a quoted JSON string. ["web",3] | @csv gives "web",3 — strings quoted, numbers bare — and @tsv gives web then a real tab then 3. Both refuse nested values: an array or object inside a row is a runtime error ("array ([\"a\"]) is not valid in a csv row"), and null becomes an empty field.

a // b produces a unless a is false, null, or produces no output at all — in which case it produces b. The trap is that it is not "if empty": 0 and the empty string are truthy in jq, so {"a":0} | .a // "fallback" is 0, not "fallback". If you specifically want "when the key is missing", test for it: if has("a") then .a else "fallback" end.

Not while the value is untouched. jq 1.8 preserves the literal you gave it, so {"n":9007199254740993} | .n prints 9007199254740993 exactly — a number JavaScript cannot represent — and 1.0 stays 1.0 rather than collapsing to 1. Do arithmetic on it and the guarantee ends: .n + 0 becomes 9007199254740992, because the maths goes through a 64-bit double. That is a jq property, not a browser one; you get the same answer from jq on the command line.

Input is capped at 2 MB (2,000,000 bytes) and the results panel renders the first 200 outputs, always with the true count next to it — "Copy all" still copies every one. A filter that never terminates is the one thing that genuinely hurts: jq runs synchronously in this tab, so it blocks the page until you reload. Whether you get an error card instead depends on the shape. If the endless stream is collected — [repeat(1)], [recurse(.a)], length, last — jq fills its WebAssembly heap and aborts after a second or two, and the playground turns that into a normal error message. Left streaming, a bare repeat(1) or recurse(.a) just keeps running: we measured no abort after 40 seconds. The two shapes to watch for are an unguarded repeat and recurse(.field), which walks onto null and then recurses on null for ever — write recurse(.field?; . != null), or wrap the generator in limit(n; …).