Suppose your training data is a giant text dump with no labels or annotations. For an LLM, that does not prevent training: self-supervised methods use the text to set prediction tasks, such as predicting the next word or a masked word. This is why many traditional labeling and feature-engineering steps are unnecessary for pretraining. section 4.3.2
No manual labels does not mean no data preparation. A practical workflow starts by defining a schema, checking whether feature distributions suit the intended outcome, looking for bias and anomalies, and converting text into model-ready form through tokenization and embedding. These are high-level considerations, not a complete data-pipeline recipe. section 4.3.2
Corpus choice brings trade-offs:
- C4 is a commonly used cleaned Common Crawl dataset for self-supervised pretraining, but cleaning does not remove inherent societal bias. section 4.3.1
- Common Crawl offers diverse web text, languages, and code, alongside the internet’s less desirable content; its available variants differ substantially in size and filtering. section 4.3.1
- OpenWebText is a smaller, 55 GB pretraining option assembled from URLs found through Reddit and filtered using karma rankings. section 4.3.1
More text alone is not a quality strategy. Large datasets can support convincing syntax without establishing semantics or pragmatics. Treat curation and informed bias checks as part of the work, even when the training targets come from the text itself. section 4.3.2
Table 4.2 Summary of datasets
|
Dataset
|
Contents
|
Size
|
Last update
|
|---|---|---|---|
|
Wikitext
|
English Wikipedia
|
<1 GB
|
2016
|
|
Wiki-40B
|
Multi-lingual Wikipedia
|
10 GB
|
2020
|
|
Europarl
|
European Parliament proceedings
|
1.5 GB
|
2011
|
|
Common Crawl
|
The internet
|
~300 GB
|
Ongoing
|
|
OpenWebText
|
Curated internet using Reddit
|
55 GB
|
2019
|
|
The Pile
|
Everything above plus specialty datasets (books, law, med)
|
825 GB
|
2020
|
|
RedPajama
|
GitHub, arXiv, Books, Wikipedia, StackExchange, and multiple version of Common Crawl
|
5 TB
|
2023
|
|
OSCAR
|
Highly curated multilingual dataset with 166 languages
|
9.4 TB
|
Ongoing
|
Compare candidate corpora by contents, size, and update date before choosing data for pretraining. section 4.3.1







