asked on December 23, 2025
Hello,
I have a report containing approximately 4 million rows. When I try to export it as a CSV, the download reaches 100% but then fails with the error shown below. The report depends on custom data source API.
Could you please help investigate this issue?
flexmonster.js:760 Uncaught RangeError: Invalid string length
at Array.join (<anonymous>)
at f.pJa (flexmonster.js:760:303)
at f.GEa (flexmonster.js:760:473)
at ff (flexmonster.js:759:138)
pJa @ flexmonster.js:760
GEa @ flexmonster.js:760
ff @ flexmonster.js:759
setTimeout
(anonymous) @ flexmonster.js:39
Hha @ flexmonster.js:79
oJa @ flexmonster.js:79
(anonymous) @ flexmonster.js:78
setTimeout
(anonymous) @ flexmonster.js:39
e.requestIdleCallback @ flexmonster.js:78
Thanks,
Berkay
⋅ December 24, 2025
Hello Berkay,
Thank you for contacting us.
This issue occurs due to the limitations of client-side CSV export in the browser. The export process is executed entirely on the client side, where Flexmonster converts the grid data into a CSV string and then saves it as a .csv file. Browsers have internal limits on string size, and when exporting large datasets, these limits can be exceeded, which causes this error: https://www.flexmonster.com/doc/typical-errors/#allocation-size-overflow-error.
To mitigate this behavior, we recommend exporting smaller data slices by filtering out unnecessary data before exporting.
Hope you will find this answer helpful.
Best regards,
Maksym
