How this works in your browser
Each file in the queue is decoded into an image object, drawn onto an off-screen canvas at either its original size or the capped size you set, and re-encoded through the browser’s own encoder at your chosen format and quality. HEIC files from an iPhone take an extra step first, since browsers cannot decode them natively, so a dedicated decoder converts them to raw pixels before the canvas stage. The ZIP is assembled in memory from the finished blobs rather than requested from a server. Because every stage runs in the tab, the constraint is your device rather than an upload limit or a queue on someone else’s machine, which is precisely why the batch is capped at ten rather than left open-ended.
Bulk Image Converter vs. traditional online converters
| Feature | Bulk Image Converter (in-browser) | Traditional online converters |
|---|---|---|
| File upload required | No - never leaves your device | Yes - file is sent to a server |
| Processing queue | None - starts instantly | Often, especially at peak times |
| Watermark on output | Never | Common on free plans |
| Usage limits | None - free, unlimited use | Often capped per day or file size |
| Works offline once loaded | Yes, for most tools | No - requires a live connection |
| Account required | No | Often, for anything beyond a trial |
Who uses Bulk Image Converter
Preparing a product gallery
Convert and size a set of listing photos in one pass instead of running the same tool ten times.
Cleaning up a phone export
Turn a folder of HEIC images from an iPhone into a format every device and platform accepts.
Meeting upload rules in bulk
Apply the same format and dimension cap across a batch so every file clears a site limit on the first try.
Handling confidential images
Process client work, ID scans or internal screenshots without any of them being uploaded anywhere.
How to use Bulk Image Converter
- 1
Open the Bulk Image Converter
Go to tools.slaytic.com and open the Bulk Image Converter. No sign-up or account required.
- 2
Drop up to 10 images
Add a mixed set if you like, since JPG, PNG, WEBP, GIF, BMP, SVG and HEIC all work as input.
- 3
Set format and quality
Choose one output format for the whole batch, then override the format or quality on any individual row that needs something different.
- 4
Add a size cap if needed
Optionally set a maximum dimension so oversized photos are scaled down proportionally during conversion.
- 5
Download the results
Save each file individually, or take everything at once as a single ZIP.
Frequently asked questions
How many images can I convert at once?
Up to 10 images per batch. If you drop more, only the first 10 are added to the queue - convert those, clear the queue, and drop the next batch.
Can each image have a different output format?
Yes. The format and quality at the top apply to the whole batch, but every image in the queue has its own format dropdown and quality slider that override the global setting for just that file.
How do I download all the converted images at once?
After converting, use the "Download all as .zip" button to save every result in a single ZIP file, or use the Download button on each row for individual files.
Are my images uploaded to a server?
No. Decoding, resizing, and re-encoding all happen locally in your browser using the Canvas API, so your images never leave your device.
Why is the limit 10 images rather than unlimited?
Because every image is decoded into memory in your browser tab, and a tab has a real memory ceiling. Ten is a batch size that stays comfortably inside it even on a phone with large photos. A queue of a hundred would look impressive right up until the tab crashed and you lost the lot.
What does the max-dimension resize actually do?
It caps the longest side of each image at the value you set, scaling the shorter side to match so nothing is distorted. Images already smaller than the cap are left alone rather than being enlarged, since upscaling only adds blur and file size.
Can I mix input formats in one batch?
Yes. JPG, PNG, WEBP, GIF, BMP, SVG and iPhone HEIC or HEIF can all sit in the same queue, and each is decoded appropriately before being re-encoded into the format you chose for it.
Which output format should I pick for a batch?
WEBP for almost anything heading to the web, since it handles photographs and flat graphics well and encodes quickly. PNG when you need exact pixels or transparency. JPG when something downstream refuses anything else.