Attach the relevant file and state the change you want. Split long briefs into tasks you can check in Preview.
Files from Google Drive or another cloud service
Download the file to your computer, then attach it with the + beside the builder message or drag the downloaded file into chat. A share link may require access the builder does not have.
Export Google Docs or Word documents as PDF or plain text, spreadsheets as CSV, and presentations as PDF. Office formats such as DOCX, XLSX and PPTX are not accepted by the chat attachment flow; convert them first. For a spreadsheet with several sheets, export the sheets you need separately.
The chat accepts supported text files, including CSV, JSON, Markdown and source code, and PDFs. Documents have a 25 MB upload limit. Images have a separate 7 MB limit and an 8,000-pixel limit on either side. A message can have up to 20 attachments in total. See Bringing your own images and SVG logos for image details.
Wait for each attachment to finish uploading before sending. If it is rejected, use the stated format or size limit to prepare a smaller supported file.
Long briefs
Start with the audience, the main task and the screens you need. Then ask for one part at a time and check Preview before continuing. Keep important requirements near the request that uses them.
An accepted upload does not mean every character will reach the model. The text-file reader truncates very large extracted text at 500,000 characters; model context and other processing limits still apply. Pasted messages have different limits. Split a long document at useful section boundaries and ask the builder to confirm the relevant requirements before it edits.
Credits
Builder turns use credits for the AI work performed. Length is one input to the cost, alongside the model, output, tools and cached context; a longer paste is not a guarantee of a larger final charge. An explanation-only request still uses a builder turn. See What uses credits.