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File upload and analysis

You can attach files directly to a chat and ask Strata to read them, summarize them, transform them, or join their contents with database results.

Supported file types

Strata accepts these formats out of the box:

  • Documents — .pdf, .docx, .doc, .txt, .md
  • Spreadsheets — .xlsx, .xls, .csv
  • Slides — .pptx, .ppt
  • Structured data — .json, .xml, .sql, .log
  • Images — .png, .jpg, .jpeg, .gif, .webp

The file picker (the + button) only lets you select files with an extension in this list. Some additional types — source code files (.py, .js, .ts, .html, .yaml, .sh), Excel macro workbooks (.xlsm), and image formats like .bmp and .svg — can be dragged in and the server will extract or pass through their content. Extensions not recognized by the server at all are rejected with an upload error rather than silently failing.

Attaching a file

Three ways:

  1. Plus button. Click the + (More options) button next to the input box and choose Add file or photo, then pick the file. You can also type / in the input box to open the slash menu and choose Attach file or photo.
  2. Drag and drop. Drag a file onto the chat area — a "Drop files here" overlay appears. Release to upload.
  3. Paste an image. With an image on your clipboard, focus the chat input and paste (Ctrl/Cmd+V).

You can attach multiple files at once and mix types — for example, an Excel workbook plus a PDF plus a reference image.

What happens during upload

Each attached file appears as a chip above the composer with the filename. While the file is being read on the server, the chip shows a loading spinner. When upload and extraction finish, the spinner disappears and the chip shows the file type and size alongside a small remove (x) button.

Strata extracts text from documents and slides on the server side so the AI can read them. For images, the binary is passed through to the AI in vision mode — the model reads the image directly, including text within it. For Excel and CSV, the AI receives the tabular content directly.

Uploads run one batch at a time. If you drag, paste, or pick more files while a batch is still uploading, Strata tells you to wait for the current files to finish rather than dropping them silently.

Each uploaded file is stored with the conversation, so you can re-open it from the chat later — it does not need to be re-uploaded for follow-up questions.

Asking questions about attached files

Once a file is attached, the AI sees it on your next message. Try:

  • "Summarize this PDF."
  • "What are the top 5 risks called out in this document?"
  • "Compare this Excel to last quarter's data in the database."
  • "Pull the totals from this CSV and chart them."
  • "What does this image show?"

You can ask several follow-up questions and the file stays in context until you remove it or start a new chat.

Combining files with other sources

Strata can mix attached files with everything else it has access to:

  • File + database — "Join the customer IDs in this CSV with our Orders table and show me the total revenue per row." Requires a SQL Server extension. See /docs/integrations/sql-server.
  • File + email — "Compare this contract draft to the version Alice sent me last week." Requires Outlook. See /docs/integrations/outlook.
  • File + OneDrive — "Find a similar file in my OneDrive Reports folder." Requires OneDrive. See /docs/integrations/onedrive.
  • File + Analysis — "Run a regression on the columns in this CSV." Strata runs the work as an analysis in its isolated sandbox. See /docs/chat/python.
  • File + Knowledge Base — "How does this draft compare to our standard contract template?" Strata can search your organization's indexed documents alongside the file you attached. See /docs/chat/knowledge-base.

Removing an attached file

Click the small x on the file chip above the composer to remove it before sending. After you send a message with a file, the file stays attached to that message in the transcript — it does not get re-uploaded for follow-ups, but the AI can still read its extracted content.

Limits and best practices

  • 20 MB per file. Each attachment is capped at 20 MB. A larger file is rejected at upload.
  • One copy per chat. If you attach a file with the same name and size as one already attached, the duplicate is rejected with a flash animation on the existing chip.
  • Server-side text extraction runs after the upload completes. For very large .docx or .pptx files this can take several seconds.
  • Long documents are trimmed. Extracted text is capped at roughly 80,000 characters per file. For a very long document, ask about the specific section you care about rather than relying on the whole file being in context.
  • Keep files focused. Strata gets more useful answers when you attach the specific file relevant to the question, not a whole folder dump.
  • Sensitive content. Files you attach are sent to the AI model the same way your messages are. All models run through your organization's own Microsoft Azure AI Foundry, so that traffic stays in your own Azure tenant. See /docs/admin/ai-engine.

What can go wrong

  • File chip shows an error. The upload or text extraction failed (network glitch, or the file is corrupt/encrypted). Remove the chip and re-attach.
  • The AI says it can't read the file. Most often this means the file uploaded but text extraction returned nothing — common for scanned PDFs that are images-of-text rather than real text. Convert to a text-based PDF first.
  • Drag-and-drop does nothing. Make sure you drop the file onto the chat area (the "Drop files here" overlay must appear). Files dropped on other pages are ignored. If a file uploads but the AI can't use it, it may be an unsupported type the server couldn't read — re-save in a supported format.

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