What is inside an SVS file
An SVS file is a TIFF with several images: the full-resolution scan (tiled, usually JPEG-compressed), a thumbnail, two or three reduced-resolution levels, a photo of the slide label and a low-magnification macro image of the whole glass. The first image's description holds the scan details, including MPP (micrometres per pixel, about 0.25 for a 40× scan and 0.5 for 20×) and AppMag. The viewer reads all of them: the pyramid drives the zoom, MPP the scale bar, and the label and macro open with the buttons beside the image.
JPEG 2000 SVS files
Some Aperio scanners compress slides with JPEG 2000 (TIFF compression 33003 or 33005). Browsers cannot decode JPEG 2000 without WebAssembly, so this page says so instead of showing a blank image. Aperio ImageScope (Windows), QuPath and SlideScope open them. To check a file first, open it in the TIFF metadata viewer and look at Compression.
The label image and patient data
The label image is a photo of the paper label on the glass and can show a barcode, case number or a patient's name. Viewing it here keeps it on your computer; sharing the file does not. See how to remove labels and patient data before sending a slide outside your institution.
What it does not open
- JPEG 2000 SVS (Aperio compression 33003/33005), JPEG XR and JPEG XL cannot be decoded in a browser without WebAssembly, which this page does not load.
- Not TIFF-based: CZI, ND2, LIF, MRXS, VSI, IMS, OIB/OIR and DICOM need a desktop reader. NDPI is TIFF-like but stores each level as one huge JPEG, too large for a browser tab.
- OME-TIFF with several series shows the first series.
- No measurements, annotations or analysis: it is a viewer.
For those formats, and for measuring, annotating and counting cells on your own images, SlideScope opens 34 microscope and slide-scanner formats on Windows and Mac. SlideScope, the desktop microscopy app made by the same team, is a paid app with a free sample library (every tool) and a 3-day free trial for your own images. Free alternatives: Fiji (Bio-Formats) and QuPath.
How it opens a file without uploading it
When you choose a file, the browser hands this page a handle to it on your disk. The page reads only the bytes it needs: the TIFF directory first, then the tiles for the part of the image on screen, and decodes them in the page with an open-source TIFF reader (geotiff). Nothing is sent to a server, so unpublished data and slides with patient labels stay on your computer, and multi-gigabyte slides open in seconds because they are never copied anywhere. Close the tab and the file is gone from the page.
The page loads its own scripts from slidescope.science and the site's privacy-respecting page-view counter; neither ever sees your image. Open-source licences: image-tools-vendor.LICENSE.txt.
Questions
How can I open an SVS file online?
Open it in this page: the browser reads the slide from your disk and shows it with zoom, the thumbnail, label and macro, and the scan details. Nothing is uploaded.
Why does my SVS file not open?
It is probably JPEG 2000-compressed (compression 33003 or 33005), which browsers cannot decode. Open it in Aperio ImageScope, QuPath or SlideScope instead.
How big an SVS file can it open?
Any size the browser can address: only the tiles on screen are read, so a 3 GB slide opens about as fast as a small one.
Does it show the slide label?
Yes, as a separate image. Keep in mind that labels can carry patient information.
Is this SVS viewer free?
Yes, it is free and needs no account. SlideScope, the desktop microscopy app made by the same team, is a paid app with a free sample library (every tool) and a 3-day free trial for your own images.
Need more than a browser can do?
SlideScope opens 34 microscope and slide-scanner formats on Windows and Mac, CZI, ND2, LIF, MRXS and JPEG 2000 SVS among them, with measuring, annotations, cell counting and full-resolution OME-TIFF export. Try every tool free on the built-in samples, then open your own images with the 3-day free trial. Already decided? Subscribe now.