How to Upload files to ChatGPT to do analysis. We are going to create a File Uploader for ChatGPT.

Uploading long documents into ChatGPT without hitting the platform’s input limits is the central workaround: instead of pasting everything at once (which triggers an error once content exceeds roughly 15,000 characters), the document is saved as a file and then automatically split into smaller chunks. Those chunks are uploaded sequentially, letting ChatGPT process the full source material and then answer questions, summarize key points, and generate conclusions grounded in the uploaded text.

The walkthrough begins with a practical example: an end-of-month report that’s too large to paste directly. The creator recommends converting the report into a text-only format—specifically copying the content into Notepad on Windows and saving it as a .txt file—because figures can complicate ingestion. After that, the file is uploaded through ChatGPT’s “Submit file” flow. During upload, ChatGPT breaks the document into parts and shows progress, indicating that the system is chunking and processing the content rather than rejecting it for being too long. Once the upload completes, follow-up prompts can be used to interrogate the report: generating a set of questions for a meeting, summarizing reading objectives, analyzing the document, drawing conclusions, and identifying challenges along with solutions. The key claim is that this approach effectively bypasses the paste limit by turning one large input into multiple smaller submissions that collectively represent the entire document.

The second half shifts from using the feature to building a reusable “File Uploader” button. A prompt is provided to ChatGPT instructing it to generate front-end code: create a “submit file” button, add a progress bar, accept specific file formats, and—critically—split files that exceed the character threshold into chunks. The code guidance also covers how to insert each chunk into ChatGPT and label it with the file name, while updating the progress bar as each part is submitted and changing its color (to blue) when all chunks finish uploading.

After generating the code, the process moves to implementation steps in a browser: inspect the page, clear console errors, inject the generated code, and verify the new button appears and can open the file explorer. To make the tool portable, the code is converted into a bookmarklet so the uploader button can be launched with a single click in future sessions. The workflow is then extended further into a Chrome extension by creating a minimal project with manifest.json and content.js, loading it via the Extensions page, and running a quick test to confirm it works.

Finally, the chunk size is presented as a tunable parameter. Smaller chunks (for example, 10,000 or even 5,000 characters) may improve accuracy but require more prompts, increasing the number of chunk submissions. The overall takeaway is that file-based chunk uploading can turn ChatGPT into a more effective analysis assistant for long reports and topic-specific reading materials, while the automation layer makes the process repeatable and shareable.