Claims with a measuring tape.
These are observed results on a Jason development machine in Chrome, not promises for every device.
Hardware, browser version, storage speed, column shape, and data type distribution all affect results.
Recorded runs
| Run | Source | Cells | First import | Cold open | Notable result |
|---|---|---|---|---|---|
| Large CSV / A | 20.97 GB | 888M | 3.9 min | 111 ms median | 0.795 GiB project |
| Billion-cell / B | 11.78 GB | 1B | 174.6 s | 93 ms median | 0 dropped frames |
How to read these numbers
First import includes parsing the CSV and writing Jason's local project. Cold open measures reopening that already-built project. These are deliberately reported separately: one is a conversion cost, the other is the recurring working experience.
What is not claimed
Jason does not claim that every 20 GB file opens on every machine, that all datasets compress by the same ratio, or that all browsers reproduce these timings. The Free plan is also capped at exactly 1,000,000,000 source bytes.
Measure it with your own file.
Open a CSV that your spreadsheet app refuses. Free covers files up to 1 GB and three local projects.