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SQuAD 2.0 — Stanford Question Answering Dataset

150K crowdsourced question-answer pairs on Wikipedia passages, including unanswerable questions.

LQS 85 · gold ✓ Commercial OK 150K Q&A pairs 40 MB JSON Released 2018
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Source: rajpurkar.github.io · maintained by Stanford NLP Group
150K
Q&A pairs
40 MB
Size on disk
85
LQS · gold
2018
First released

About this dataset

SQuAD 2.0 combines 100K questions from SQuAD 1.1 with 50K unanswerable questions adversarially written by crowdworkers. Answers are spans of text from Wikipedia passages. It's the canonical benchmark for extractive question answering and reading comprehension.

Maintainer
Stanford NLP Group
License
CC BY-SA 4.0
Formats
JSON
Paper
Read on arxiv.org →

LabelSets Quality Score

LQS is our 7-dimension quality score, computed from the dataset's published statistics. See methodology →

85
out of 100
gold tier

High-quality dataset across most dimensions

Composite score computed from the 7 dimensions below: completeness, uniqueness, validation health, size adequacy, format compliance, label density, and class balance.

Completeness 95
No public completeness metric; using prior for 'expert_curated' datasets.
Uniqueness 93
Exact-hash deduplication documented by maintainer.
Validation 82
Crowdsourced labels with quality-control protocol (redundancy, golden tests).
Size adequacy 91
150,000 pairs — exceeds 100,000 adequacy target for NLP / Text.
Format compliance 95
Industry-standard format — drop-in compatible with mainstream tooling.
Label density 52
Average 1.0 labels per item (sparse).
Class balance 75
Moderate class skew — realistic production distribution.

What it's used for

Common tasks and benchmarks where SQuAD 2.0 — Stanford Question Answering Dataset is the default or competitive choice.

Sample statistics

What's actually in the dataset — from the maintainer's published stats.

150,000 questions total: 100K answerable + 50K unanswerable. ~23.2 words avg per question, ~3.2 words avg per answer span.

License

SQuAD 2.0 — Stanford Question Answering Dataset is distributed under CC BY-SA 4.0. This is a third-party public dataset; LabelSets indexes and scores it but does not host or redistribute the data. Always verify current license terms with the maintainer before commercial use.

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Similar public datasets

Other entries in the NLP / Text catalog.

The Pile
300M documents · MIT (mixed sub-licenses)
C4 — Colossal Clean Crawled Corpus
365M documents · ODC-BY
Wikipedia (English Dump)
6.8M articles · CC BY-SA 4.0
MS MARCO
8.8M passages · MS MARCO License (research only)

Frequently Asked Questions

SQuAD 2.0 — Stanford Question Answering Dataset is distributed under CC BY-SA 4.0, which generally permits commercial use. Always verify the current license terms with the maintainer (Stanford NLP Group) before using in a commercial product.
SQuAD 2.0 — Stanford Question Answering Dataset contains 150,000 Q&A pairs. 150,000 questions total: 100K answerable + 50K unanswerable. ~23.2 words avg per question, ~3.2 words avg per answer span.
SQuAD 2.0 — Stanford Question Answering Dataset is maintained by Stanford NLP Group and is available at https://rajpurkar.github.io/SQuAD-explorer/. LabelSets indexes and scores this dataset for discoverability but does not redistribute it.
LQS is a 7-dimension quality score (completeness, uniqueness, validation, size adequacy, format compliance, label density, class balance) computed from the dataset's published statistics. Composite scores map to tiers: platinum (≥90), gold (≥75), silver (≥60), bronze (<60). Read the full methodology.