📚 ClassiCC-PT: Classified Common Crawl Corpus for Portuguese

📖 Overview

ClassiCC-PT (Classified Common Crawl – Portuguese) is a large-scale web corpus containing ~120B Portuguese tokens extracted from Common Crawl snapshots. It is specifically curated for training large language models in Portuguese, with a focus on data quality, language specificity, and targeted filtering.

This corpus was created as part of a study on continued pretraining for adapting English-trained LLMs to Portuguese.

🏗 Dataset Construction

Source Snapshots: CC-2021-31, CC-2021-39, CC-2022-40 Steps:

• Language Filtering

  Selected only pages tagged with Portuguese in Common Crawl metadata (~2% of each CC crawl).
  

• HTML to Text Extraction

  Used Trafilatura to remove boilerplate and extract main content.
  

• Deduplication

  Applied MinHash intra-crawl deduplication (removing ~40% duplicates).
  

• Neural-Based Filtering

  Developed three BERTimbau-based classifiers for:
  
  Educational content (ClassiCC-PT-edu)
  
  STEM content (ClassiCC-PT-STEM)
  
  Toxic content (ClassiCC-PT-toxic)
  
  Classifiers were  trained on GPT-4o-annotated Portuguese data.
  

Final Corpus

Retained ~106M documents / ~125B tokens ( Llama 2 tokenizer)

🚀 Performance Impact

When used for continued pretraining of TinyLlama-1.1B (1T EN tokens), ClassiCC-PT improved Portuguese benchmark performance (Poeta v1) significantly, outperforming mC4-PT and matching ClueWeb-22-PT. The model trained with ClassiCC-PT is called Curió 1.1B and is available at huggingface.

Model	Training Regimen	Poeta v1 NPM
TinyLlama-1T (EN)	–	17.4
mC4-PT	cont. pretraining	~20
ClueWeb-22-PT	cont. pretraining	~27
ClassiCC-PT (Curió-1.1B)	cont. pretraining	27.1

📥 Download & Usage

from datasets import load_dataset

ds = load_dataset("ClassiCC-Corpus/ClassiCC-PT", split="train")

print(ds[0])

# {
# 'text': '...',
# 'id': '...',
# 'url': '...',
# 'edu_score': 4.0,
# 'stem_score': 1.0,
# 'toxic_score': 0.0
# }

📜 Citation

If you use ClassiCC-PT, please cite:

@article{almeida2025building,
  title={Building High-Quality Datasets for Portuguese LLMs: From Common Crawl Snapshots to Industrial-Grade Corpora},
  author={Almeida, Thales Sales and Nogueira, Rodrigo and Pedrini, Helio},
  journal={Journal of the Brazilian Computer Society},
  volume={31},
  number={1},
  pages={1246--1262},
  year={2025}
}

Acknowledgements

We thank the google TRC program, which generously granted us the necessary resources for the development of this research.