Meilisearch ranking: a multi-criteria system beyond BM25

How Meilisearch’s multi-criteria ranking system works, why it produces better results than BM25 for user-facing search, and the technical trade-offs involved.

Most search engines rank results using a single relevancy score computed from a formula like BM25 or term frequency. Meilisearch takes a fundamentally different approach: it evaluates multiple ranking criteria sequentially, giving you transparent control over what matters most and delivering results that feel right to end users.

How traditional search ranking works

Single-score ranking models

Traditional search engines compute a single numeric score per document, then sort by that number. The two most common approaches are:

BM25 (Elasticsearch, OpenSearch, Lucene, MongoDB Atlas Search) is the industry standard for full-text search. It scores documents based on:

• Term frequency (TF): How often the query term appears in the document
• Inverse document frequency (IDF): How rare the term is across all documents
• Document length normalization: Shorter documents get a slight boost

PostgreSQL ts_rank is a simpler model used by PostgreSQL full-text search (and Supabase). It uses term frequency with optional document length normalization, but does not consider inverse document frequency. PostgreSQL also offers ts_rank_cd (cover density), which factors in proximity of matched terms. Both are less sophisticated than BM25.

In all cases, the engine produces a score like 8.72 or 3.14, and results are sorted by this number in descending order.

The problem with single-score ranking

BM25 was designed for information retrieval, finding research papers, legal documents, or web pages where term frequency genuinely signals relevance. But for application search (e-commerce, media catalogs, SaaS dashboards), this model breaks down:

• Typos are invisible: BM25 treats “iPhone” and “iPhoone” as completely different terms. The misspelled query returns zero results
• Word order is ignored: Searching “dark knight” and “knight dark” produce identical scores, even though user intent clearly favors the first ordering
• Field importance is flattened: A match in a product title should matter more than a match in a review comment, but BM25 requires manual field boosting that’s fragile and hard to tune
• Scoring is opaque: A score of 8.72 means nothing to a developer debugging why result A appears before result B
• Prefix matching requires workarounds: A user typing “prog” expects to see “programming”, but BM25 doesn’t do this without additional analyzers

How Meilisearch ranks results

Meilisearch replaces the single-score model with a multi-criteria bucket sort system. Instead of computing one number, it evaluates documents through a sequence of ranking rules, each acting as a successive filter.

The ranking pipeline

When a user searches for "badman dark knight returns", Meilisearch applies ranking rules in order:

All matching documents
  │
  ├─ 1. words ──────────── How many query words match?
  │     ├─ 4/4 words → Bucket A
  │     ├─ 3/4 words → Bucket B
  │     └─ 1/4 words → Bucket C
  │
  ├─ 2. typo ───────────── How many typos were needed?
  │     ├─ 0 typos → Sub-bucket A.1
  │     └─ 1 typo (badman→batman) → Sub-bucket A.2
  │
  ├─ 3. proximity ──────── How close are matched words?
  │     ├─ Adjacent → Sub-bucket A.1.1
  │     └─ 3 words apart → Sub-bucket A.1.2
  │
  ├─ 4. attributeRank ──── Which field matched?
  │     ├─ Title → higher
  │     └─ Overview → lower
  │
  ├─ 5. sort ───────────── User-defined sort (if any)
  │
  ├─ 6. wordPosition ───── Where in the field did it match?
  │     ├─ Start of field → higher
  │     └─ End of field → lower
  │
  └─ 7. exactness ──────── Exact match or partial?
        ├─ Exact → higher
        └─ Prefix/partial → lower

Each rule only operates on documents that tied in all previous rules. This means:

• A document matching 4/4 words with 2 typos always ranks above a document matching 3/4 words with 0 typos
• The words rule has absolute priority over typo, which has absolute priority over proximity, and so on
• There is no way for a high score in one dimension to compensate for a low score in another

This is called lexicographic ordering, the same logic humans use to sort words in a dictionary, applied to search ranking.

The seven default ranking rules

Order	Rule	What it measures	Why it matters
1	words	Number of query terms matched	Documents matching more of what the user typed are more relevant
2	typo	Number of typos corrected	Exact matches are preferred, but typos still return results
3	proximity	Distance between matched terms	”dark knight” in sequence beats “dark … knight” far apart
4	attributeRank	Which attribute matched	A title match is more important than a description match
5	sort	User-defined sort order	Only active when the query includes a sort parameter
6	wordPosition	Position of match within the attribute	Matching at the start of a title beats matching at the end
7	exactness	Exact match vs prefix/typo match	”knight” exactly beats “knights” (prefix)

You can reorder, add, or remove any of these rules. You can also add custom ranking rules that incorporate business logic, like boosting newer products or higher-rated items.

Why this is better for application search

1. Typo tolerance is built in

BM25 either matches a term or it doesn’t. Meilisearch’s typo rule is a first-class ranking criterion: documents matching with fewer typos rank higher than those requiring more corrections, but all of them appear in results.

Query	BM25	Meilisearch
"iphone"	Returns iPhone results	Returns iPhone results
"iphoen"	0 results	Returns iPhone results (1 typo)
"ipohne"	0 results	Returns iPhone results (2 typos)

2. Word order and proximity matter

BM25 treats a document as a bag of words: the position and distance between terms don’t affect the score. Meilisearch’s proximity rule ensures that documents where query terms appear close together and in order rank higher.

Query: "new york pizza"	BM25	Meilisearch
”Best New York pizza places”	Same score as below	Ranks 1st (adjacent, in order)
“New restaurant in York with great pizza”	Same score as above	Ranks 2nd (words spread apart)

3. Field importance is explicit and predictable

With BM25, field boosting requires numeric weights (title^3 description^1) that interact unpredictably with term frequency and document length. In Meilisearch, the attributeRank rule uses the order of searchableAttributes: the first field always wins over the second, no math involved.

// searchableAttributes setting
["title", "brand", "description"]

A match in title always outranks a match in description (assuming previous rules tied). No weights to tune, no interactions to debug.

4. Ranking is transparent and debuggable

BM25 produces opaque scores. Meilisearch lets you inspect exactly why a document ranks where it does using showRankingScoreDetails:

{
  "title": "Batman: The Dark Knight",
  "_rankingScoreDetails": {
    "words": { "order": 0, "matchingWords": 3, "maxMatchingWords": 3 },
    "typo": { "order": 1, "typoCount": 0, "maxTypoCount": 3 },
    "proximity": { "order": 2, "score": 0.98 },
    "attributeRank": { "order": 3, "score": 1.0, "attributeRankingOrderScore": 1.0 },
    "exactness": { "order": 6, "score": 0.67 }
  }
}

You can see that this result matched 3/3 words, with 0 typos, high proximity, in the highest-ranked attribute. If a result appears in the wrong position, you can identify which rule caused it and adjust.

5. Prefix search works natively

When a user types "prog" in a search bar, they expect to see “programming”, “progress”, “program”. BM25 requires n-gram tokenizers or edge-gram analyzers to achieve this. Meilisearch handles it automatically: the last word in a query is always treated as a prefix.

6. No per-query tuning required

BM25 deployments often require extensive per-query tuning: function scores, field boosts, decay functions, script scores. Meilisearch’s ranking rules are configured once at the index level and work consistently across all queries. The same rules that rank “batman” well also rank “comfortable running shoes” well.

Trade-offs to be aware of

Meilisearch’s approach is optimized for application and site search. There are scenarios where BM25 may be more appropriate:

Scenario	BM25	Meilisearch
Log analytics	Better (term frequency matters for finding error patterns)	Not designed for this use case
Academic paper search	Better (TF-IDF identifies topically relevant papers)	Optimized for short, user-facing queries
Documents > 10KB	Handles naturally	Best with documents split into smaller chunks
Custom scoring formulas	Fully customizable via script scores	Fixed rule set with configurable order
Billions of documents	Horizontally scalable	Designed for millions of documents per index

Combining ranking with semantic search

Meilisearch’s ranking system works alongside hybrid search. When you enable an embedder, Meilisearch combines keyword-based ranking (the rules above) with vector similarity in a single query:

{
  "q": "comfortable running shoes",
  "hybrid": {
    "semanticRatio": 0.5,
    "embedder": "default"
  }
}

The semanticRatio controls the blend: 0.0 uses only the multi-criteria ranking rules, 1.0 uses only vector similarity, and values in between merge both result sets. This gives you the best of both worlds, BM25-beating keyword relevancy plus semantic understanding, without managing two separate search systems.

Summary

	BM25 / ts_rank (Elasticsearch, PostgreSQL, etc.)	Meilisearch multi-criteria ranking
Approach	Single numeric score per document	Sequential bucket sort through multiple rules
Typo handling	None (or via fuzzy query, separate step)	Built-in, ranked by typo count
Word proximity	Not a factor in BM25; basic in PostgreSQL ts_rank_cd	Dedicated ranking rule
Field importance	Numeric boosts with complex interactions	Ordered list, first field always wins
Prefix search	Requires analyzer config (BM25) or :* syntax (PostgreSQL)	Automatic on last query word
Debuggability	Opaque score	Per-rule breakdown via showRankingScoreDetails
Configuration	Per-query function scores and boosts	Per-index rules, consistent across queries
Semantic search	Separate system (kNN, vector DB, pgvector)	Integrated via hybrid parameter
Best for	Log analytics, research, large corpora	Application search, e-commerce, media catalogs

Learn more

• Ranking rules: Configure and reorder the seven built-in rules
• Bucket sort: How the bucket sort algorithm works
• Ranking score: Understanding the 0.0–1.0 ranking score
• Custom ranking rules: Add business logic to ranking
• Ordering ranking rules: Best practices for rule ordering