AI Writing Detector
Suspect a passage was written by AI? Check it without uploading a word.
Formula Worksheet Maker
Custom math worksheets with auto-graded answer keys and printable certificates.
Banner Maker
Need a social banner without signing into Canva? Design and export PNG locally.
Form Maker Plus
Bulk PDFs from a CSV — without a backend or coding.
Form Maker
Need a fillable PDF form without Acrobat? Drag, fill, export A4.
QR Maker
Free QR codes from any URL, with color options and no tracking pixel.
Frequently Asked
Are these tools free?
Yes. Every Single Page Sandbox tool is completely free — no paywall, no premium tier, no in-app purchase. The download is gated only by a free Substack newsletter subscription.
Do they need an account or signup?
No. None of the tools require an account, login, or sign-in to use. The Substack subscription is for the newsletter, not for the tools themselves — you can also click "Already a subscriber" and proceed.
Does my data upload anywhere?
No. Every tool processes your text, images, and CSV files entirely inside the browser. Nothing is uploaded to a server. The site uses analytics internally to improve the experience — no content of what you type or generate is ever transmitted.
Can I use them offline?
Most tools are, unless indicated otherwise. Each tool is a single HTML file. After you download the zip, extract home.html and open it directly in your browser — works fully offline with no internet connection.
Why locally runnable web pages?
Because the browser is the most universal runtime there is. A single HTML file bundles presentation, interactivity, and logic into one document that runs on practically any device — Windows, Mac, Linux, phone or tablet — with nothing to install. And it's no toy format: serious products like Figma and Google Docs run entirely in the browser. Running a tool locally, as a file you own, means no vendor lock-in, no subscription, and no handing your data to someone else's server — your work stays on your machine.
Who builds and maintains these?
Nirav Bhatt at Brain Bound Learning. New tools and how-they-work deep-dives are posted on the Substack publication.
Are they safe to run?
We try our best to make them safe. But we don't control the state of the user's machine, so we don't bear any legal liability for running them locally. See our Terms.