View NIfTI files in your browser
The format of brain research, from MRI and fMRI to PET. Open a scan right here and step through it in every plane. Nothing leaves your device.
Or drop it anywhere on this page
What you'll see
Your scan opens slice by slice, with its series or planes beside it, what the scanner says in its corners and the patient's sides at its edges.
- Every series in order through the body • The wheel steps through it
- Window and level • Drag it, or pick CT's presets
- Measure lengths, angles and areas in millimeters
- Export • PNG, JPEG, MP4, or the files without patient data
About NIfTI
NIfTI came out of the US National Institutes of Health in 2004 to give brain imaging tools one format. FSL, SPM, AFNI, FreeSurfer, ITK-SNAP and 3D Slicer all read and write it, and so does every converter that turns a scanner's DICOM files into one tidy volume, like dcm2niix.
A NIfTI file is a header and a block of voxels, most often gzipped as .nii.gz. The header gives the volume's size, its voxels' spacing and where it sits in the scanner, so left stays left. NIfTI-2 takes bigger volumes, and the older Analyze 7.5 keeps the header in a .hdr and the voxels in an .img beside it.
Filepeek reads the volume in your browser and cuts it into axial, coronal and sagittal slices without resampling, with the patient's sides at the edges. Step through with the wheel or the arrow keys, set the window and level, measure in millimeters, read every header field, and save a slice as PNG or JPEG or a plane as MP4. A series over time shows its first volume.
Neuroimaging Informatics Technology Initiative
.nii
Format
- MIME type
- application/x-nifti
- Made by
- The NIfTI Data Format Working Group, at the NIH
- Released
- 2004
Inside the file
- Header
- 348 bytes, or 540 in NIfTI-2
- Voxels
- 8 to 64 bit, integer or float
- Dimensions
- 3D, or 4D over time
- Placement
- Where each voxel sits in the scanner
- Packing
- Plain, or gzipped as .nii.gz
Opens in every browser
Browsers download NIfTI files. Filepeek opens them in Chrome, Edge, Firefox and Safari, gzipped or not.
- YouChromeOpens through Filepeek
- YouEdgeOpens through Filepeek
- YouFirefoxOpens through Filepeek
- YouSafariOpens through Filepeek
Questions
How do I open a .nii.gz file?
Drop it on this page as it is. Filepeek unpacks it in your browser and opens the volume.
Which planes can I see?
All three: axial, coronal and sagittal, each listed beside the image. Pick one and step through its slices with the wheel, the arrow keys or the slider.
Does it open Analyze .hdr and .img files?
Yes. Drop the .hdr and the .img together, and the volume opens from its header.
Is my scan uploaded?
No. It opens inside your browser and never leaves your device.