How to use Lumo
- Open a folder, watch for new images, and save copies.
- Turn automatic processing on or off.
- Build an output set with the sizes you need.
- Understand each size, format, and quality setting.
- Share a folder workflow with an AI agent.
- Change language, check for updates, or clear a workspace.
Which files can I use?
Lumo accepts still JPEG, PNG, WebP, supported HEIC and HEIF photos, and SVG files. You can save photos as WebP, AVIF, JPEG, or PNG. SVG files stay SVG.
AVIF is an output format only: you can't add an AVIF file as a source image. Lumo doesn't process video or Live Photo sequences.
A photo can be up to 25 MB and 40 megapixels, with neither side longer than 16,383 pixels. SVG files can be up to 5 MB. Each batch accepts up to 100 files and 100 MB of source data. Use smaller batches if you reach a limit.
If a HEIC photo won't open, export a JPEG from your photo app and add that instead. See the HEIC conversion guide for format and color limitations.
My images are waiting or failed
Adding images and changing settings don't start processing by default. Choose Process when you're ready.
If one image fails, read its error message. Other images in the batch can still finish. Check that the original opens in another image viewer and is within the file limits above. For a large job, try fewer images in a new batch.
If Lumo reports a browser feature is missing, update your browser. Folder access has separate requirements, described below.
The result is larger or looks wrong
An image that's already compressed may not get smaller. A PNG copy of a photo can also be larger than a JPEG or WebP copy. Compare the file size and appearance before deciding which to use.
For a soft-looking photo, try Best quality or a larger size limit, then process again. Lumo doesn't enlarge an image beyond its original dimensions.
When you create multiple sizes, the batch total includes all the generated files. That total is different from the size of one image a visitor will download.
If JPEG processing fails for an image with a transparent background, choose WebP, AVIF, or PNG. JPEG can't keep transparency, and Lumo won't add a background for you.
Where are my saved images?
Open Export to download the results or save them to a folder. Downloads go to the location chosen by your browser. Check its downloads list if you can't find them.
Download requested means Lumo handed the file to your browser. It can't check that the browser finished saving it. If you downloaded a ZIP, extract it to get the individual images.
Folder saves go to the location you selected. For an open source folder, Save to optimized puts copies in its optimized subfolder. Wait for the saved confirmation before closing Lumo.
If only part of a manual folder save finishes, keep Lumo open. Resolve the error, then open Export and retry the unsaved files. For a failed automatic save, use Retry saving. You can also download the prepared results.
I can't open or save to a folder
Direct folder access needs browser support and your permission. If the folder picker isn't available, use Add images and download your results. You can also try a current desktop version of Chrome or Edge.
If access was denied or has expired, choose Allow access when Lumo offers it. Check that the folder is still available, especially on a removable drive.
Folder watching checks for new files while Lumo is open and visible. It pauses when the page is hidden or closed. Use Refresh to pick up changes to files already in the folder. Images in subfolders aren't included.
Auto-process & save is optional. It prepares images and saves copies to optimized after you allow write access. When you return to a saved session, automation and watching start paused.
Returning to unfinished work
Lumo saves unfinished work in this browser when storage is available. Reopen the app in the same browser and profile. You can find other unfinished sessions in Settings.
If work hasn't returned, check whether you used another browser or cleared the app's site data. Private browsing and browser storage cleanup can also remove saved work. Export important results to files instead of relying on recovery.
If Lumo says it can't save recovery data, keep the app open and export your results before clearing anything. Your original files and previously exported copies are separate from browser storage.
Using Lumo offline
Open the published Lumo app online first. It downloads the files it needs for offline use after the page loads. Before relying on it away from a connection, try reopening it offline with a small test image. After setup, you can prepare images and download results without a connection.
If offline loading stops working, reconnect and open Lumo again. Clearing site data can remove the files it needs for offline use.
Still need help?
Contact Kreativiq with your browser, device, the file type, and the error message. Describe what you tried and what happened. You don't need to send the original image to start.