ChatGPT 5.1 File Upload and Reading: formats, limits, analysis tools, and what the new update can actually do

ChatGPT 5.1 did not introduce new file types or a brand-new upload system, but it dramatically changed how well the assistant handles large documents, spreadsheets, PDFs, ZIP archives, and multi-file analysis. The improvements come from the model’s adaptive reasoning, higher context stability, and faster internal planning, not from a new interface. This makes the 5.1 upgrade feel smoother and more reliable in real workflows: longer documents load more consistently, PDF summaries maintain structure, and multi-file comparisons are more coherent than before.

Because these changes come from the model rather than the UI, many users don’t understand what 5.1 can or can’t do with uploaded files. This article clarifies the full picture: supported formats, size limits, tool behaviors, what 5.1 improves, and the strict capabilities that still depend on the underlying tools rather than the model itself.

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ChatGPT 5.1 works with all existing file tools.

GPT-5.1 supports every file-related tool that previous GPT-5/4o models used: Data Analysis, document analysis, image analysis, ZIP extraction, structured outputs, and advanced Python-based workflows. Nothing was removed.

The only technical exception is GPT-5.1 Pro, a reasoning-intensive variant that does not support Canvas or image generation, but it still supports file uploads, data analysis, and PDF/document reading as usual.

This means: any workflow you could perform under GPT-5, GPT-4o, or GPT-5 Pro is available with 5.1 — only faster and more structurally reliable.

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The full list of supported file types with ChatGPT 5.1.

ChatGPT 5.1 supports a wide range of formats across documents, spreadsheets, data, code, archives, and images.

Documents:PDF, DOCX, RTF, TXT, Markdown, EPUB, ODT

Presentations:PPT, PPTX

Spreadsheets & Data:XLS, XLSX, CSV, JSON, XML, HTML tables, IPYNB

Code files:PY, JS, TS, CSS, JSX, SQL, YAML, TOML, C, C++, Java, PHP, and most plaintext code formats

Images:PNG, JPG/JPEG, WEBP, GIF

Archives:ZIP files (ChatGPT extracts and analyzes contents automatically)

Cloud-linked files:Google Drive and OneDrive documents (imported into the workspace for analysis)

Limitations:

• .gdoc cannot be uploaded directly — it must be exported as PDF or DOCX.

• Encrypted PDFs cannot be read unless decrypted externally.

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File size, token limits, and daily quotas that apply to 5.1.

These limits are tool-level and apply regardless of whether you choose GPT-5.1 Instant or Thinking.

• 512 MB maximum per file (any type).

• ≈ 2 million token maximum text extraction per file — large PDFs may truncate internally.

• Images up to 20 MB each.

• Spreadsheets up to ~50 MB, depending on row/column density.

• ZIP files up to 512 MB total, with internal extraction limits applying per file.

• User upload quotas:

• Paid plans: up to 80 uploads every 3 hours

• Free plan: 3 files per day

• Custom GPTs: up to 20 files attached as persistent knowledge

• Storage limits:

• 10 GB per end-user

• 100 GB per organization

These limits have not changed due to 5.1 — but 5.1 handles large files more efficiently inside these boundaries.

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What ChatGPT 5.1 can do with uploaded files: the expanded capabilities.

GPT-5.1 improves almost every type of file analysis because the model is more stable, less prone to misalignment, and more efficient in multi-step reasoning. The capabilities below work through Data Analysis, document comprehension, sandboxed Python, and tool routing.

1. With spreadsheets and CSV files

GPT-5.1 can:

• read, clean, filter, join, and merge datasets

• generate charts (bar, line, scatter, histograms, box plots)

• run statistical analysis, regressions, and forecasts

• build dashboards, pivot summaries, and KPI breakdowns

• write Python code using pandas, numpy, scipy, statsmodels

• detect outliers, correlations, clusters, and patterns

• export cleaned or transformed datasets for download

Its faster adaptive reasoning means it now responds more quickly on large spreadsheets and reduces false assumptions around column structure.

2. With PDFs, Word files, and long documents

GPT-5.1 can:

• summarize entire PDFs with better section structure

• extract clauses, lists, tables, footnotes, and figures

• compare multiple documents (contracts, reports, research papers)

• locate mentions of keywords across hundreds of pages

• rewrite, reformat, condense, or translate sections

• generate structured outputs like tables, timelines, policy summaries

GPT-5 often struggled with long PDFs, especially when table formats varied; GPT-5.1 maintains context more reliably across multi-section and multi-document workflows.

3. With ZIP archives

ZIP uploads allow ChatGPT 5.1 to analyze:

• entire codebases

• multi-file datasets

• collections of PDFs or mixed formats

GPT-5.1 extracts and reads the contents automatically, then lets you navigate files individually, compare them, refactor code, or generate full project summaries.

4. With images

When images are uploaded directly (not inside a PDF), GPT-5.1 can:

• describe visual content

• perform OCR (extract on-image text)

• interpret charts, UI screenshots, signs, and diagrams

• compare multiple images side-by-side

Inside PDFs, however, images are treated as text-only unless using Enterprise with visual retrieval.

5. With code files and multi-file workflows

GPT-5.1 is the strongest file-editing model so far thanks to:

• apply_patch for surgical code edits

• more reliable generated diffs

• fewer malformed JSON tool calls

• more consistent multi-step reasoning across codebases

This makes upgrading or refactoring a folder of code much more stable than under GPT-5.

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What ChatGPT 5.1 still cannot do with uploads.

Some limitations are tool-inherent and unchanged by GPT-5.1:

• Cannot open .gdoc files directly — export first.

• Cannot process encrypted PDFs until unlocked.

• Cannot run external APIs through Python — outbound network requests are blocked.

• Cannot modify cloud files in place (Drive, OneDrive) — it outputs new versions instead.

• Cannot fully parse ultra-large PDFs beyond the 2M token extraction limit.

• Cannot analyze images inside PDFs unless on Enterprise with visual retrieval.

• Cannot read proprietary binary formats from unsupported apps.

These restrictions apply to all GPT-5 generation models, including 5.1.

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What GPT-5.1 improves behind the scenes when reading files.

The biggest improvements are behavioral rather than structural:

• Better long-context retention across multi-section documents

• Faster page-level comprehension thanks to adaptive reasoning

• More accurate table extraction from PDFs

• Fewer hallucinations in document summaries and cross-document comparisons

• More reliable multi-file synthetic outputs (e.g., combining 5 PDFs into one structured report)

• Better Python code generation for advanced data analysis tasks

• Cleaner narrative structuring in summaries, outlines, and reports

GPT-5 could occasionally lose coherence across long chains of document reasoning; GPT-5.1 maintains structure far more consistently.

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GPT-5.1 continues the same file-handling capabilities as prior models but strengthens every stage of the workflow: faster comprehension, more stable reasoning, smoother data processing, and fewer breakdowns when handling complex multi-file or multi-step tasks. The tools remain the same — but the experience is significantly upgraded. For users who work with contracts, research papers, spreadsheets, data models, or codebases, 5.1 is a noticeably more powerful file-analysis engine.

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