🗂️ Files and conversions: the lossless guide
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Converting a PDF, shrinking a photo, opening a strange file… Here's how to do it without losing quality or exposing your data.
1. Pick the right format
| Need | Recommended format | Avoid |
|---|---|---|
| Photo to share | JPG (80–90% quality) or WebP | PNG (too heavy for photos) |
| Logo, screenshot, image with transparency | PNG or WebP | JPG (no transparency, blurry edges) |
| iPhone photo received as HEIC | Convert to JPG for compatibility | |
| Document to send or print | Word, if the layout must stay identical | |
| Document to edit | DOCX / ODT | PDF (hard to edit) |
| Data table | CSV (simple) or XLSX (formulas) | A screenshot of a table |
| Many files to send | ZIP | 20 separate attachments |
2. Shrink files without ruining quality
- Photos: lowering the resolution saves far more than lowering quality. A 4000 px photo resized to 1600 px stays sharp on screens and is about 6 times smaller.
- PDFs: a heavy PDF almost always contains large images. Compress the images inside (150 dpi is enough for screens, 300 dpi for print).
- Videos: going from 1080p to 720p roughly halves the size.
- ⚠️ Every re-save of a JPG loses a little quality. Always keep the original.
3. Offline or online? Think privacy
Online converters upload your file to a server. For an ID card, a payslip, a contract or medical records, prefer an app that converts on the phone, offline.
Simple rule: if you wouldn't post this file on Facebook, don't upload it to an unknown conversion website.
4. Where are my files?
- Downloads:
Download/ - Camera photos:
DCIM/Camera/ - Screenshots:
Pictures/Screenshots/orDCIM/Screenshots/ - WhatsApp:
Android/media/com.whatsapp/WhatsApp/Media/ - Since Android 11, other apps'
Android/data/folders are no longer accessible. That's normal: it's a protection.
5. Never lose a file again: the 3-2-1 rule
- 3 copies of your important files,
- on 2 different media (phone and computer or USB drive),
- with 1 copy away from home (cloud).
Turn on automatic photo backup and check once a month that it actually works.
6. Good habits
- Start file names with the date:
2026-10-17_electricity_bill.pdf. They sort themselves. - A password-protected ZIP should use AES-256 encryption, not the old "ZipCrypto".
- To free up space, start with videos and the WhatsApp folder: they're usually the biggest.
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