Open
Import a CSV into a browser-local project without uploading the file to Jason.
Product / 01
Big files become working files.
Jason is a browser spreadsheet engine for CSV datasets that exceed the practical limits of ordinary spreadsheet apps.
| A | B | C | D | E | F | |
|---|---|---|---|---|---|---|
| 1 | txn_id | posted_at | account | amount | fee | balance |
| 2 | 418002998 | 2026-07-02 | ACC-1037 | 19.73 | 0.37 | 814.47 |
| 3 | 418003005 | 2026-07-03 | ACC-1074 | 27.06 | 0.51 | 1117.06 |
| 4 | 418003012 | 2026-07-04 | ACC-1111 | 34.39 | 0.65 | 1419.65 |
| 5 | 418003019 | 2026-07-05 | ACC-1148 | 41.72 | 0.79 | 1722.24 |
| 6 | 418003026 | 2026-07-06 | ACC-1185 | 49.05 | 0.93 | 2024.83 |
| 7 | 418003033 | 2026-07-07 | ACC-1222 | 56.38 | 1.07 | 2327.42 |
| 8 | 418003040 | 2026-07-08 | ACC-1259 | 63.71 | 1.21 | 2630.01 |
| 9 | 418003047 | 2026-07-09 | ACC-1296 | 71.04 | 1.35 | 2932.60 |
| 10 | 418003054 | 2026-07-10 | ACC-1333 | 78.37 | 1.49 | 3235.19 |
| 11 | 418003061 | 2026-07-11 | ACC-1370 | 85.70 | 1.63 | 3537.78 |
| 12 | 418003068 | 2026-07-12 | ACC-1407 | 93.03 | 1.77 | 3840.37 |
| 13 | 418003075 | 2026-07-13 | ACC-1444 | 100.36 | 1.91 | 4142.96 |
| 14 | 418003082 | 2026-07-14 | ACC-1481 | 17.69 | 0.34 | 730.26 |
| 15 | 418003089 | 2026-07-15 | ACC-1518 | 25.02 | 0.48 | 1032.85 |
SUM 41,882,004.19ROWS 166,666,666LOCAL PROJECT — NOT UPLOADED
From source file to reusable project
Work
Search, sort, edit, calculate, and navigate the full dataset through a responsive canvas grid.
Return
Reopen the local project without paying the original import cost again.
Export
Write the result back to CSV when the work is done.
Architecture / local-first
The product is split where trust should be split.
The spreadsheet engine reads and transforms data in the browser. Commercial services handle only account, payment, and signed licence state. File rows do not need to cross that boundary.
- Import
- Browser-local processing into a persistent local project.
- Grid
- Canvas rendering keeps the visible surface small and responsive.
- Calculation
- Computed locally; advanced calculated columns are a Pro capability.
- Licence
- Short-lived, signed receipt that is verified by the product.
Do not shrink the question to fit the tool.
Open a CSV that your spreadsheet app refuses. Free covers files up to 1 GB and three local projects.