Why is my TIFF bigger after clipping or exporting from QGIS?

A smaller map area does not always mean a smaller TIFF. If an export writes uncompressed pixels, it can outweigh the compressed source. Recast can rewrite a readable TIFF with DEFLATE compression while keeping its resolution.

By Recast · Published 8 September 2026

Why a smaller crop can produce a larger file

File size depends on more than the number of pixels. Compression, the number of bands, data type, and auxiliary data can all affect the result. A crop reduces the pixel count, but changing from compressed storage to uncompressed storage can offset that reduction.

In a historical QGIS clipping question, a user reported a 375 MB source becoming a roughly 900 MB output. That illustrates the symptom; it is not a benchmark for Recast or a claim about the defaults in every current QGIS tool.

First, inspect what changed

• Compression: compare the source and exported TIFF. Recast shows the compression reported by GDAL.
• Dimensions and bands: an export may contain more pixels or bands than you expected.
• Data type: storing values with a wider numeric type can require more bytes per pixel. Recast’s band details appear in the metadata.

If the export changed the resolution, bands, or type unnecessarily, revisit the export settings in QGIS. Recast’s compatibility rewrite retains those properties; it does not choose a smaller numeric type or downsample the image.

Try a lossless compression rewrite

1. Keep the original export so you can compare it with the result.
2. Select the TIFF in Recast. Include its matching .tfw if it relies on one.
3. Review the detected dimensions, band information, compression, and georeferencing.
4. Choose GeoTIFF and click Make compatible with QGIS. Recast writes tiled, DEFLATE-compressed TIFF data.
5. Download the result and compare file sizes. Open it in QGIS to check its position, resolution, bands, and nodata areas before replacing anything.

The GDAL GeoTIFF documentation describes the compression and tiling options used for this kind of rewrite. Recast uses DEFLATE; it does not currently provide a compression-method picker.

When the result may be larger

Smaller output is not guaranteed. Already-compressed TIFFs may not benefit. Replacing lossy JPEG compression with lossless DEFLATE can increase file size substantially. Tiling and metadata also affect the result. Use this workflow when conventional lossless storage fits the job, not as a promise to shrink every raster.

Lossless compression preserves the decoded values, but it cannot undo earlier lossy compression. Recast verifies key output metadata after reopening the result; keep the source and inspect the output for your intended use.

What about multi-gigabyte orthophotos?

Recast accepts up to 1 GB total input per batch and limits estimated decoded raster pixels and retained downloads to 1 GB each. Browser memory can run out before those limits. A highly compressed image can expand far beyond its on-disk size. Use desktop GDAL or QGIS for larger datasets; see current limits.

Compression is different from faster map rendering

Reducing storage size does not by itself guarantee faster display. Recast writes tiles, but it does not build overview pyramids or promise Cloud Optimized GeoTIFF output. If your main problem is slow zooming and panning, a desktop workflow with suitable overviews may be more useful.

For decoder failures rather than file size, read the JPEG library error guide. For the general rewrite workflow, see making a GeoTIFF compatible with QGIS.