About Twinpage and how we test it

What the app does

Twinpage takes a PDF, .docx, .doc or .rtf file, or a photo of a paper page (Pro), and returns a PDF that looks like the original in another language, plus an editable .docx on request. It uses the translator built into iOS, on the phone, with no account and no upload. It runs on phones with iOS 26 or later. It gives machine translation and does not certify anything; see machine or certified translation.

How we test

• October 26, 2026. .docx translation checked with automated tests on a Mac (27 tests): after translation the file has the same parts and the same number of paragraphs, tables and cells. Run on 6 test files and 14 .docx files from a document corpus.
• October 26, 2026. PDF modes checked on a corpus of 15 PDF files, including a scanned 71-page order, with a stand-in translator that makes text 25% longer. No failures; pages checked by eye. 31 automated tests passed on a Mac.
• October 26, 2026. App tests for the daily limit, the 3-page limit, Pro, samples not counting toward the limit, and an accessibility audit of the screens.
• October 27, 2026. The translator built into iOS run on a Mac with the app's engine: English to Spanish 7.0 s, English to Russian 2.1 s, Spanish to English 2.1 s, Russian to English 1.3 s. Layout kept; errors noted.
• October 29, 2026. First run on a real phone (iOS 27.2): sample contract from English to Spanish in 217 s including language preparation. Table, bold labels and columns in place.

Errors we found are published, not hidden: Details of the parties became Detalles de las fiestas, and Qty and Amount both became Cantidad. The full list of runs is on the languages page.

What is not tested yet

• Any pair other than English to Spanish on a real phone.
• Results in Arabic, Hindi, Thai, Chinese, Japanese and Korean, checked by eye.
• A real English scan translated on a phone.
• Size and time of the first language download on a phone.
• Long documents and background work on a phone.

Contact

Questions, errors in a translation or a document that came out wrong: write to {email}. Please do not attach private documents. Help with subscriptions and data is on the support page.