Claude AI File Upload and Document Reading

Claude AI has developed advanced file upload and reading capabilities that make it a flexible tool for managing documents, data, and visual content. The features range from simple uploads in chat to persistent knowledge bases within projects, with specific limits, supported formats, and processing rules. In late 2025, these functions have become more refined and integrated with additional modes, including file creation and editing.

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File types supported by Claude AI.

Claude accepts a wide range of document and data formats. Among textual documents it supports PDF, DOCX, TXT, HTML, ODT, RTF, EPUB, and JSON. For structured data files it handles CSV natively, while XLSX files are accepted if the analysis tool or the upgraded file creation and analysis feature is enabled.

In addition, Claude can read image files in JPEG, PNG, GIF, and WEBP formats, with a maximum size of 30 MB and resolution up to 8000 × 8000 pixels. This extends the assistant’s use cases to tasks that involve visual or graphic content, within the limits of the active model.

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Upload limits and size restrictions.

The usage limits are clearly defined. In chat, Claude allows up to 20 files per conversation, with a maximum of 30 MB per file. In projects with knowledge bases, the file size remains limited to 30 MB, but the number of files is unlimited. However, the extracted content from these files must fit within the context window of the active model, which represents the effective constraint on how much can be processed in a single request.

These thresholds make Claude suitable both for single-document analysis and for handling larger collections, provided they are segmented appropriately.

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How Claude reads and processes files.

The way Claude processes content depends on file type and model capabilities. For PDFs under 100 pages, with models such as Claude 4, Claude 3.7 Sonnet, and Claude 3.5 Sonnet, the visual mode is enabled: the assistant can interpret not only text but also images, charts, and embedded tables. For PDFs longer than 100 pages, or when using models without visual mode, only the text is extracted.

For non-PDF files, such as DOCX, TXT, or CSV, Claude extracts and reads text only, ignoring embedded images. This means that diagrams or graphics should be uploaded separately as image files if they need to be analyzed.

Within project knowledge bases, uploaded files are indexed and made persistently available as context. This allows cross-referenced and cumulative questions to be asked across entire document collections, maintaining consistency in long workflows.

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Context window and processing capacity.

Claude offers a very large context window. Standard consumer and API versions provide over 200,000 tokens of context, already sufficient for very large documents. With Claude Sonnet 4, available in beta with dedicated pricing, the context window can extend to 1,000,000 tokens, enabling the analysis of complex, multi-document archives in a single session.

These values make Claude one of the most powerful tools for large knowledge base work, though it remains important to optimize document structure for targeted queries and accurate results.

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File creation and editing capabilities.

Beyond reading, Claude has introduced file creation and editing features directly within its interface. Users can generate and save .xlsx, .docx, .pptx, and .pdf files, either locally or connected to cloud services such as Google Drive.

This evolution transforms Claude from a reading-only assistant into a complete document lifecycle tool, integrating drafting, editing, and reading within a single environment.

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Strengths and practical limitations.

Claude excels in multi-file management, format flexibility, and visual analysis of smaller PDFs. The integration into project knowledge bases also enables structured and persistent workflows.

The main limitations appear with PDFs over 100 pages, where only text is extracted, and with non-PDF files, where embedded images are not processed. Even with its wide context window, there is still a capacity threshold that requires attention when working with extensive content.

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Summary table of limits and capabilities.

Feature	Specification
Maximum file size	30 MB
Number of files in chat	20
Number of files in projects	Unlimited (30 MB each)
Textual formats	PDF, DOCX, TXT, HTML, ODT, RTF, EPUB, JSON
Data formats	CSV, XLSX (with analysis tool)
Image formats	JPEG, PNG, GIF, WEBP
Image limits	30 MB, up to 8000 × 8000 px
PDFs under 100 pages	Text + images
PDFs over 100 pages	Text only
Standard context window	200,000+ tokens
Extended context window	Up to 1,000,000 tokens (Sonnet 4)
File creation	.xlsx, .docx, .pptx, .pdf

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Operational considerations.

Effective use of Claude for file upload and reading requires some practical steps. Large documents should be divided to stay within context limits, images and charts should be provided as separate files when needed, and projects should be used to maintain continuity across complex analyses.

With these practices, Claude positions itself as a versatile tool for businesses, researchers, and professionals needing to work with heterogeneous and large-scale document collections.

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