Custom software · In-house product
DonExcel
An Excel course where you don't watch: you write.
- Client
- In-house product
- Year
- 2026
- What we did
- Product, brand, development and content
- Live
- donexcel.com
The starting point
In an Excel skills test, nobody asks you what VLOOKUP is: they hand you a spreadsheet and a clock.
There was nothing useful for preparing in Spanish: English-language material uses different function names. DonExcel was built for that. It's an administration and accounting course where students write every formula in a spreadsheet inside the browser and get it marked instantly, cell by cell.
Our involvement
- Concept and syllabus
- Brand
- App design
- Development
- Formula engine
- Lessons and exercises
- Payments and accounts
- Search engine optimisation
What we did
- 01
Our own formula engine
It understands 148 Excel functions by their Spanish and English names, and spills dynamic arrays just like Excel. It doesn't stop at the result: it checks that the formula holds up with other data and can be dragged down, and when it fails it explains why.
- 02
Exercises that never repeat
Practice templates generate new data on every attempt, and projects change their figures. You can't memorise the answer: you have to know how to get it.
- 03
Certificates anyone can verify
Whatever counts towards the certificate is marked on the server, which rebuilds the spreadsheet with the same data and the same engine. Each certificate can be verified through a link.
- 04
Guides that teach by doing
Thirty public guides on formulas, errors and Excel tests, with free exercises to practise without signing up.
Technology
- App
- A single HTML fileNo build step and no dependencies: nothing to break between the editor and the server.
- Engine
- Our own JavaScriptThe same engine marks in the browser and on the server.
- Hosting
- NetlifyThe website and the server functions that protect the paid content.
- Accounts and data
- SupabaseStudents, progress and certificates.
- Payments
- StripeOne-off card payment.
- ResendThe platform's emails, sent from servers in the European Union.
- Quality
- Playwright and axe-coreThirty test suites, accessibility included, on every change.
148Excel functions the engine understands
92lessons
100practice templates
30automated test suites