Understanding the Solr JSON Response

Ask with wt=json and every answer of your index is built from the same parts. This is what each one holds.

01 · The parts

Part	When	What it holds
`responseHeader`	Always	`status` 0 means success. `QTime` is the time Solr spent, in milliseconds, network not included.
`response`	Always, unless there is an error	`numFound` (all the matches), `start` (the offset you asked for), `maxScore` (when `fl` asks for the score) and `docs`, the results of this page.
`highlighting`	`hl=true`	Snippets with the searched words marked, keyed by document id: Highlighting.
`facet_counts`	`facet=true`	Counts per value: Facets.
`spellcheck`	`spellcheck=true`	Corrections: Did you mean.
`error`	On failure	The reason and the HTTP code.

02 · A result

{
  "id": "1f9e6cba8357fe106a950a1f80b301cc",
  "uri": "https://www.example.com/blog/solar-panels",
  "title": "Solar Panels for Small Roofs",
  "description": "How many panels fit on a small roof, and what they produce.",
  "og_image": "https://www.example.com/img/solar.jpg",
  "meta_domain": "example.com",
  "meta_detected_language": "en",
  "content_type": "text/html",
  "creation_date": "2026-09-14T08:30:00Z",
  "score": 0.853
}

A result carries the fields named in fl; score is there only when fl asks for it. What each field holds: the core fields and the fields Opensolr adds to every document.

03 · Facets

Each facet is a flat list of value, count, value, count:

"facet_counts": {
  "facet_fields": {
    "meta_detected_language": ["en", 834, "de", 245, "fr", 123]
  }
}

var pairs = data.facet_counts.facet_fields.meta_detected_language;
var facets = [];
for (var i = 0; i < pairs.length; i += 2) {
  facets.push({ value: pairs[i], count: pairs[i + 1] });
}

With json.nl=map in the request, the same facet comes back as an object instead: {"en": 834, "de": 245}.

04 · Did you mean

"spellcheck": {
  "suggestions": ["bakup", {"numFound": 3, "startOffset": 5, "endOffset": 10, "suggestion": ["backup", "backups", "baked"]}],
  "collations": ["collation", "solr backup", "collation", "solr backups"]
}

collations alternates the word collation with a whole corrected search; the first one is collations[1].

05 · Errors

{
  "responseHeader": { "status": 400, "QTime": 36 },
  "error": {
    "metadata": ["error-class", "org.apache.solr.common.SolrException", "root-error-class", "org.apache.solr.common.SolrException"],
    "msg": "undefined field nonexistent_field",
    "code": 400
  }
}

The HTTP status of the answer is the same code. 400 means the request is wrong (syntax, a field that does not exist, a bad value); 401 means the username or password is wrong; 500 is an error inside Solr, and your Error Log shows it.