LongFact

LongFact evaluates factual precision over long-form generations containing many individual claims. Each claim is extracted and verified, and the model is scored on claim-level precision, measuring whether extended responses introduce unsupported or false statements.

MAI-Thinking-1 from Microsoft currently leads the LongFact leaderboard with a score of 0.980 across 1 evaluated AI models.

Paper
About this benchmark

What LongFact measures

LongFact is a text benchmark that evaluates large language models on factuality and general tasks. LLM Stats tracks 1 model on this benchmark, with a maximum possible score of 1. Current average across reported models is 1.0, with the leader reaching 1.0.

Compare leaders on the best AI for factuality and best AI for general leaderboards.

Publication

Paper
Long-form factuality in large language models
Authors
Jerry Wei, Chengrun Yang, Xinying Song, Yifeng Lu, and 8 others
Published

Abstract

Large language models (LLMs) often generate content that contains factual errors when responding to fact-seeking prompts on open-ended topics. To benchmark a model's long-form factuality in open domains, we first use GPT-4 to generate LongFact, a prompt set comprising thousands of questions spanning 38 topics. We then propose that LLM agents can be used as automated evaluators for long-form factuality through a method which we call Search-Augmented Factuality Evaluator (SAFE). SAFE utilizes an LLM to break down a long-form response into a set of individual facts and to evaluate the accuracy of each fact using a multi-step reasoning process comprising sending search queries to Google Search and determining whether a fact is supported by the search results. Furthermore, we propose extending F1 score as an aggregated metric for long-form factuality. To do so, we balance the percentage of supported facts in a response (precision) with the percentage of provided facts relative to a hyperparameter representing a user's preferred response length (recall). Empirically, we demonstrate that LLM agents can outperform crowdsourced human annotators - on a set of ~16k individual facts, SAFE agrees with crowdsourced human annotators 72% of the time, and on a random subset of 100 disagreement cases, SAFE wins 76% of the time. At the same time, SAFE is more than 20 times cheaper than human annotators. We also benchmark thirteen language models on LongFact across four model families (Gemini, GPT, Claude, and PaLM-2), finding that larger language models generally achieve better long-form factuality. LongFact, SAFE, and all experimental code are available at https://github.com/google-deepmind/long-form-factuality.

MicrosoftMAI-Thinking-1 leads with 98.0%.

Progress Over Time

Interactive timeline showing model performance evolution on LongFact

State-of-the-art frontier
Open
Proprietary

LongFact Leaderboard

1 models
ContextCostLicense
11.0T
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FAQ

Common questions about LongFact.

What is the LongFact benchmark?

LongFact evaluates factual precision over long-form generations containing many individual claims. Each claim is extracted and verified, and the model is scored on claim-level precision, measuring whether extended responses introduce unsupported or false statements.

What is the LongFact leaderboard?

The LongFact leaderboard ranks 1 AI models based on their performance on this benchmark. Currently, MAI-Thinking-1 by Microsoft leads with a score of 0.980. The average score across all models is 0.980.

What is the highest LongFact score?

The highest LongFact score is 0.980, achieved by MAI-Thinking-1 from Microsoft.

How many models are evaluated on LongFact?

1 models have been evaluated on the LongFact benchmark, with 0 verified results and 1 self-reported results.

Where can I find the LongFact paper?

The LongFact paper is available at https://arxiv.org/abs/2403.18802. The paper details the methodology, dataset construction, and evaluation criteria.

What categories does LongFact cover?

LongFact is categorized under factuality and general. The benchmark evaluates text models.

How recent are the LongFact leaderboard results?

The LongFact leaderboard was last updated in June 2026 and currently includes 1 evaluated models.

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