How much you can trust Bublio
Bublio grades a child's work, so it should have to earn your trust. This page sets out the detail: what the scanner does when it isn't sure, exactly how it is tested and what it scored, what your school needs to get the best from it, and what happens to your data.
What happens when Bublio isn't sure
Every answer the scanner reads gets one of two outcomes: a mark it is confident about, or a question that comes back to you. That is not a guess with a warning attached — no score is claimed for that question until a person decides it.
Bublio says which question and what it saw: two marks on question 8, a bubble that looks erased and answered again, a mark too faint to call. You get the reason and a cropped photograph of that exact spot on the paper, so you decide from the evidence rather than from our description of it.
This is a rule in the codebase, not a setting: unclear reads always come back to a person, never resolved by picking the most likely answer.
Getting the best from it
- Clear what needs you before you release: each one opens on the cropped photograph of that question, so a stack of them is minutes rather than an afternoon.
- Clean prints and dark pens leave less for you to check — the print and scan test in Bublio proves both in five minutes, before a class depends on them.
How we test the scanner
The scanner is exercised against sheets generated from the same geometry the real printed sheet uses, then degraded to look like real phone photographs: photographed at an angle, rotated, unevenly lit, blurred, noisy, JPEG-compressed and shrunk. Answers are marked in several different hands — solidly filled, heavy, light pencil, ticks and crosses — and some are erased and answered again.
The test then compares every single answer against what was drawn, and separates two kinds of mistake: one that came back to a person, and one that did not. The second kind is the only one that can quietly change a report, so it is the number we watch.
What it scored
From the run on 2026-07-29, on 200 generated sheets carrying 3,919 answers:
- Answers read exactly right
- 3,896 of 3,919 (99.4%)
- Read wrongly, but flagged for a person
- 22
- Read wrongly WITHOUT being flagged
- 1 — about 1 in 3,919
- Sheets refused as unreadable rather than guessed
- 1 of 200
- Printed student numbers read exactly right
- 199 of 200
Read the second and third rows together: when the scanner was wrong, it nearly always said so. That is the behaviour to judge it on — an unflagged mistake is the only kind that can reach a report without a person seeing it.
Getting the best from it
- The sheets are generated from the product's own geometry and then degraded on purpose — angled, rotated, unevenly lit, blurred, compressed — so the run is harder than a careful photograph of a real paper.
- Two things at your end carry the accuracy across: print at 100% scale with 'fit to page' off, and keep all four corner squares inside the photo. Bublio's own print and scan test proves both in five minutes.
Scanning without internet
The reading happens on your phone, so a dead connection does not stop you scanning. Sheets you scan while offline are held on the device and sent when the connection returns, and the screen tells you how many are still waiting.
Each capture carries its own key, created the moment the sheet is read. That is what makes a retry safe: however many times a sheet is re-sent — after a crash, a lost reply, a closed tab — it can only ever become one result, never two grades for one paper.
Getting the best from it
- The score appears the moment a waiting sheet is sent — the answer key never travels to the phone, which is why the marking happens where the key is.
- Let the waiting sheets finish sending before closing the tab or clearing the browser: the screen always shows how many are still waiting, so it takes a glance.
What you actually need
A printer, ordinary paper, and a phone with a camera. Bublio makes the answer sheet as a PDF, you print it on plain paper, and the phone reads it back. There is no special form to order, no dedicated scanner, and nothing to install on a school computer.
The four black squares in the corners are how the sheet is located in a photograph, which is why the printing instructions matter more than the paper does.
Getting the best from it
- Print at 100% scale, with 'fit to page' or 'shrink to fit' turned off. This one setting decides more first scans than anything else.
- Keep all four corner squares fully inside the photo. Bublio refuses a sheet it cannot locate rather than grading it from a partial view — and says so.
- Print from Bublio where you can, and copy from the original where you cannot: dark, clean sheets read fastest and leave the least to check.
Where your data lives, and how you get it out
Student names, exams and scanned images belong to your school. You can export results as CSV, Excel or a PDF report at any time, and delete exams, students and scanned images from inside the app. Deleting a school account permanently removes its data, including student information and scanned images.
Personal data is never sold, and student data is never used for advertising. Answer keys never travel to the scanning device — the phone reads which bubbles are filled, and the marking happens where the key is.
A complete copy of your school's data is taken every night, including every scanned answer sheet — the images are inside that copy, so one copy is the whole thing.
At worst, a failure costs a single day: the work between the last nightly copy and the moment of the fault. The restore is rehearsed on a separate copy, and the drill checks that a whole school opens with its grades matching — not merely that the tables are there. Every rehearsal is recorded in a log.
Getting the best from it
- Export before you delete: CSV, Excel and the PDF report are always one click away, and a deletion is permanent by design.
- A school administrator sees the exams and results of teachers at that school — deliberately, so a school keeps oversight of its own grades. The infrastructure Bublio runs on is named in the privacy policy.
- Ask for the drill log: the rehearsal that proves a backup restores is recorded each time it is run, with the date, how long it took and what was checked.
Arabic and right-to-left
This website works in Arabic, right to left, and the printed answer sheets render Arabic properly: the letters join into their correct forms and the text runs in the right direction, which most PDF tools get wrong.
It applies to every field a teacher types — the exam title, the subject, section headings and each student's own name on a personalized sheet.
Getting the best from it
- Type the exam title, subject, class and student names in Arabic and they print as typed — joined and right to left, which most PDF tools get wrong.
- Switch language with the toggle at the top of any public page; the printed staffroom guides come in both.