As developers, we end up needing to convert or resize a file constantly — a screenshot that needs to be a PNG for docs, an asset that needs to hit exact social-preview dimensions, a PDF that needs merging before a demo. Reaching for ffmpeg, imagemagick, or a paid SaaS every time is overkill for a one-off task. Here are two free, no-signup web tools that cover most of that day-to-day friction.
1. FreelyConvert — general-purpose file conversion
A browser-based converter covering documents, images, video, and audio:
500+ formats — PDF, DOC/DOCX, images (JPG/PNG/GIF/BMP/SVG/WEBP), video (MP4/AVI/MOV/MKV), audio (MP3/WAV/FLAC/AAC), spreadsheets, presentations
No account/signup — upload, convert, download
Batch conversion for multiple files in one pass
Auto-delete after 24 hours and SSL encryption in transit
Useful specifically for:
- PDF ↔ image conversions (
pdf-to-jpg,images-to-pdf) - Merging PDFs without touching a CLI tool
- Compressing video/audio for quick sharing
- Quick image compression when you don't want to script it
2. ImageResizer.dev — client-side image resizing/conversion
This one's worth calling out for devs specifically: it runs entirely client-side via the Canvas API — nothing is uploaded to a server. That's a real difference if you're resizing anything you'd rather not send off-device, and it also means it's fast (no upload/download round trip).
Features:
Exact dimension presets for social platforms (Instagram, LinkedIn, X/Twitter, YouTube, TikTok, Pinterest, WhatsApp) — handy for generating OG images or social preview assets without hardcoding dimensions yourself
Format conversion across JPG, PNG, WebP, AVIF, BMP, GIF, SVG
Crop, flip, upscale, plus bulk resize/compress for batches
Aspect-ratio locking to avoid distortion- No account, no watermark
Good fit for generating og:image assets, favicon prep, or resizing screenshots for a README without spinning up a script.
Why bother mentioning these
Neither requires an account, neither is trying to upsell a subscription, and the second one is architecturally interesting since it avoids the upload step entirely by processing in-browser. Bookmarking both saves the "let me write a quick script for this" tax for genuinely repetitive/batch work, while one-offs stay a browser tab away.
Links:
SOCIAL SHARE CARD GENERATOR