I put 64 file tools and an open-weight AI model in a browser tab. Nothing gets uploaded.

Description and use

On Android, Fizzdoc’s PDF split tool was slow due to many small reads by qpdf; copying the file into memory up to 128 MB fixed the issue, matching laptop speed.

Problem

On Android phones, Fizzdoc’s PDF split tool took six minutes due to many small file reads by qpdf, causing poor performance.

Outcome

Performance on Android improved from six minutes to near‑instant split, matching laptop speed for small files, while maintaining privacy guarantees.

Workflow

• Open Fizzdoc on Android
• Select PDF file
• Choose split tool
• qpdf reads file in many small chunks via WORKERFS
• Performance suffers
• Implement copy‑up‑to‑128‑MB logic
• Read file once into memory
• qpdf processes file
• Download result

Evidence

On a laptop the same kind of job took about a second.

Source

What I didn’t know: qpdf doesn’t ask for a few big pieces. It asks for lots and lots of tiny ones.

Source

On a 10 MB, 28-page test PDF, I counted 1,448 separate reads

Source

Same test file: 1,448 reads became zero, and even on my laptop the split went from 1.4 s to 0.25 s.

Source