Exact match and string presence

Exact match and string presence are RAGAS metrics that compare the response with the reference as plain strings, with no judge model, and return 1 or 0.

Last updated: 29 Sep, 2026 · RAGAS 0.4.3

Most RAGAS metrics ask a model to judge. These two do not, so they cost nothing and give the same answer every time. They are the quickest way to see what a metric is: something that takes fields of a sample and returns a number.

The ExactMatch and StringPresence API

from ragas.metrics.collections import ExactMatch, StringPresence

ExactMatch().score(response=..., reference=...)      # 1.0 only if the two strings are identical
StringPresence().score(response=..., reference=...)  # 1.0 if the reference appears inside the response

The reference for g005

The price golden has one exact fact. Take the price itself as the reference.

reference = "$899"

Two answers to score

answers = ["$899", "The PixelPhone 15 is priced at $899."]

Scoring two price answers

from ragas.metrics.collections import ExactMatch, StringPresence

exact = ExactMatch()
present = StringPresence()
reference = "$899"

for answer in ["$899", "The PixelPhone 15 is priced at $899."]:
    print(answer)
    print("   exact match   ", exact.score(response=answer, reference=reference).value)
    print("   string present", present.score(response=answer, reference=reference).value)

$899
   exact match    1.0
   string present 1.0
The PixelPhone 15 is priced at $899.
   exact match    0.0
   string present 1.0

Why the full sentence fails exact match

• Exact match compares the two strings character by character. The full sentence is the better answer and still scores 0, which is why judged metrics exist.
• String presence asks whether the reference appears inside the answer. Both answers contain $899, so both score 1.
• The score sits in .value. Every RAGAS metric returns a result object, not a bare number.

Exact match vs string presence

When to use string metrics

• A fact with one correct form, such as a price or a SKU, that must appear in the answer.
• A required sentence, such as a warranty disclaimer, that every answer must carry.

Related

• Previous: SingleTurnSample
• Next: ID-based context precision and recall
• Reference: Traditional metrics