ISO maker — folder to disc image
Tool for creating ISO disk images directly in your browser. Pick a folder, set a volume label, optionally add a boot image — and download a standards-compliant ISO9660+Joliet image. With the hybrid MBR option the result also boots from a USB stick written with `dd`.
How to build an ISO
Click "Pick folder" to open the system folder picker, or use Add files to assemble a manual list.
Enter a volume label (max 32 chars) and optional publisher.
Drop a BIOS/UEFI boot image and tick Hybrid MBR if you want a USB-bootable ISO.
showSaveFilePicker opens; choose where to save the ISO.
The image streams to disk; progress shows the build phase as it runs.
Pack any directory into a downloadable ISO disk image
Why this builder is special
ISO creator — common questions
Will my ISO boot from a USB stick?
Yes, when you provide a boot image and tick Hybrid MBR. The output gets a valid El Torito record (for BIOS/UEFI from optical media) and a hybrid MBR so dd if=image.iso of=/dev/sdX produces a bootable USB.
Why is the ISO bigger than the folder it came from?
Because an ISO stores everything in sectors of 2048 bytes and a file never gets to share one. A 100-byte file occupies a whole sector, and a file of 5000 bytes occupies three — so a folder of many small files grows noticeably, while a folder of a few large ones barely changes. The directory records and the Joliet name table add a little on top. This is a property of the format rather than an inefficiency to be tuned away: it is what lets any reader find a file by seeking straight to a sector instead of parsing its way there.
Can the ISO be larger than the memory on this machine?
Yes, because it is never assembled in memory. You choose the destination file first, and the image is then written to it sector by sector as the folder is walked — so an 8 GB image is produced with a working set of a few megabytes, and the ceiling is free disk space rather than RAM. The source side works the same way: the folder is read through the browser's folder picker, one file at a time, so a directory tree with tens of thousands of entries streams past rather than being held.
Are filenames case-preserving?
Yes when Joliet is enabled. Joliet stores the original Unicode names case-preserved; ISO9660 also has 8.3 forms for legacy compatibility.
How do I make the image bootable?
Add a boot image and say whether it is for BIOS or UEFI; a valid El Torito boot record is then written into the ISO, which is the structure firmware looks for when it decides whether a disc can be started from. That covers optical media and virtual machines. For a USB stick there is the hybrid MBR option on top: it puts a partition table at the very front of the image as well, so the same file works both as an ISO burned to a disc and as something written byte-for-byte to a stick — which is how installer images are usually distributed today.
Can I rebuild an ISO from a slightly modified folder?
Yes. Pick the modified folder, keep the same volume label, and build again. Future versions will include a diff-and-update mode that preserves the original PVD metadata.
Will my ISO open on macOS / Linux / Windows?
Yes. ISO9660 is supported by every major operating system; Joliet adds Windows-friendly long names; Linux mounts the result with mount -o loop.
We can! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.
