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How to burn an ISO from a USB drive to a disc
If you have an ISO file sitting on a USB stick, you can write it straight to a disc - no need to copy it locally first. cdBurner reads the .iso from wherever it lives and burns it sector-for-sector so the disc is bootable or readable as intended.
An ISO file is a single-file snapshot of an entire disc — its files, its layout and any boot data. To use it you don't copy the file onto a disc; you burn the image, which recreates the original disc sector for sector. That's why a properly burned ISO can boot a PC or install an operating system.
What you'll need
- A Windows 10 or 11 PC with a CD, DVD or Blu-ray writer (internal or external USB).
- A blank disc big enough for the image — a CD for small images, a DVD up to 4.7 GB, a Blu-ray for more.
- The .iso stored on your USB drive.
- The free cdBurner burn agent — a one-time, 2-second install.
Quick facts
- Burns an .iso from any drive Windows can see
- No need to copy the file to your hard disk first
- Written as a true disc image, not a file copy
Step by step
Connect the burn agent
Open onlinecdburner.com and make sure the burn agent is connected (install it once if needed).
Insert a blank disc big enough for the image
Match the disc to the image size — a CD for small images, a DVD for up to 4.7 GB, a Blu-ray for more.
Choose “ISO image”
Select the .iso stored on your USB drive.
Burn the image
cdBurner writes it sector-for-sector so the disc is bootable/readable exactly as intended. Keep Finalize on.
Tips for a clean burn
- Write the ISO as an image, never as a file copy — only an imaged disc boots or behaves like the original.
- Match the disc to the image: CD up to 700 MB, DVD up to 4.7 GB, dual-layer 8.5 GB, Blu-ray 25 GB+. cdBurner shows the fit before you start.
- Leave Finalize on so the disc is closed and reads everywhere.
Common mistakes to avoid
- Copying the .iso onto the disc as a file instead of writing the image — the disc won't boot.
- Choosing a disc that's too small for the image.
- Burning a bootable disc at maximum speed on cheap media, which can corrupt it.
Why cdBurner is different
Unlike Nero, ImgBurn or the others, cdBurner needs no heavy software — just a 2-second helper, and your files never leave your PC.
- 100% free — no trial, no watermark, no nag screens.
- Private — files are written locally and never uploaded to a server.
- No bloatware — one small signed helper, not a heavy install.
- Built on Windows' native IMAPI2 engine, so your discs read everywhere.
Frequently asked questions
Will the burned disc be bootable?
If the ISO is a bootable image, yes — cdBurner writes it sector-for-sector and keeps the boot data intact, so the disc boots exactly like the original.
Can't I just copy the ISO file onto the disc?
No. Copying the .iso as a file gives you a disc with one file on it. You must burn the image so the disc becomes what the ISO represents.
Is cdBurner really free?
Yes — completely free and ad-supported. No trial, no watermark and no paid tier.