Spreadsheet Viewer
Open an uploaded spreadsheet in the browser with its sheets and headers intact.
What it adds
An in-app read-only viewer for uploaded spreadsheet and delimited files, with sheet tabs and frozen headers.
What your agent is told to do
5
What your agent is told to do
5-
1
Reuse the app's existing file preview surface and Attachment Gallery entry points so a spreadsheet opens where every other file type opens, rather than in a separate viewer page.
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2
Parse on the server and send the viewer only the rows it currently needs. Shipping an entire workbook to the browser will stall the tab on any file of real size.
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Build on the app's existing table components, including its sticky header and frozen column behaviour, instead of a second grid implementation.
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4
Keep it read-only and say so. If the app has a CSV Import, link to it from the viewer for anyone who wants the data in the app rather than quietly adding editing here.
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5
Do not evaluate formulas. Show what the file recorded and be explicit when a value could not be resolved.
Edge cases it handles
8
Edge cases it handles
8- A sheet with a hundred thousand rows or three hundred columns will freeze the browser if every cell is rendered. Virtualize in both directions and keep scroll position stable as rows load.
- Files often store a formula alongside its last computed value, and files written by other tools may store neither. Show the cached value where one exists, show the formula text where it does not, and never show an error token as if it were data.
- Plain text files arrive with semicolons, tabs, or pipes as separators and in encodings other than UTF-8, and guessing wrong produces one column of mojibake. Detect delimiter and encoding, show what was detected, and let the user override it.
- Merged cells and frozen header rows drift out of alignment as soon as rows are virtualized or columns are resized. Measure them explicitly rather than assuming a uniform row height.
- Past a defined row or cell ceiling the viewer should decline clearly and offer the original file for download instead of attempting the render and timing out.
- Spreadsheets carry hidden sheets, hidden columns, and cell comments that the uploader may not know are there. Decide whether to surface them and be consistent, rather than exposing them by accident.
- Dates, currencies, and percentages lose their meaning when rendered as raw serial numbers. Apply the recorded cell format, and render numbers right-aligned so columns read as columns.
- A corrupt, password-protected, or macro-bearing file must fail with a specific message, and macros must never be executed or offered.
Definition of done
9
Definition of done
9- An uploaded spreadsheet opens in the app with its sheets selectable and headers frozen.
- Very long and very wide sheets scroll smoothly with rows and columns virtualized.
- Cached values are shown where formulas cannot be evaluated, and unresolvable cells are marked as such.
- Delimiter and encoding are detected for text files, displayed, and overridable.
- Merged cells and frozen headers stay aligned while scrolling and resizing.
- Files past the row ceiling are declined with a download offered instead.
- Dates, currencies, and percentages render using the recorded cell format.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
PDF Converter
PDF Converter
Let people turn the files they upload into PDFs, and PDFs back into editable formats.
What it does
A conversion service that accepts an uploaded document and returns it in a requested format, with progress and a downloadable result.
How it works
- 1 Start from the app's existing upload path rather than adding a second one. If File Upload, Upload Malware Scanning, or Secure File Downloads already exist, the converter consumes what upload produces and hands its output to the existing download route, so permissions and scanning are inherited rather than reimplemented.
- 2 Decide the conversion pairs you will actually support and list them in the interface. A short honest list of office documents, images, and PDF to text beats a control that offers every combination and fails on most of them.
- 3 Enforce file size, page count, and accepted types on the server before any conversion starts. A limit checked after the file has been parsed has already cost you the memory and the CPU you were trying to protect.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/pdf-converter
Fillable PDF Forms
Fillable PDF Forms
Let people fill in a PDF form on screen and download the completed copy.
What it does
An on-screen fill layer over a PDF form that writes the entered values back into a downloadable file.
How it works
- 1 Render the document and place editable inputs over its real form fields, so the user types on the page they recognise rather than into a separate form beside it.
- 2 Extend the app's existing PDF Export and document viewing paths rather than introducing a second renderer. Two renderers will disagree about fonts and page size, and the user will see the difference between screen and download.
- 3 Save progress as the user types using the app's existing Autosave, and restore the partly filled form on return.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/fillable-pdf-forms
Document Scanner
Document Scanner
Turn a phone photo of a paper document into a straight, readable, multi-page file.
What it does
A camera capture flow that detects page edges, corrects perspective, and assembles the shots into one document.
How it works
- 1 Lead with the capture screen: live edge detection, a shutter, and a running strip of the pages already taken. Somebody should be able to shoot five pages without leaving the camera.
- 2 Correct perspective and crop to the detected page before saving, then apply a contrast pass so a grey photo of a page reads as black text on white.
- 3 Give the user a review step where pages can be reordered, retaken, or deleted before anything is committed.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/document-scanner
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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2
Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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3
It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.