When to use this tool
Stitch satellite scene clips
When your AOI spans two Sentinel-2 UTM tiles or two Landsat path/rows, the satellite downloader produces one clip per scene. Bring them here to combine them into a single GeoTIFF covering the full AOI.
Mosaic DEM tiles
Government DEMs (SRTM, USGS 3DEP, EU-DEM) are distributed as 1°×1° or smaller tiles. Drop in all the tiles covering your study area and get a single seamless surface model.
Combine drone flight outputs
When a drone job is split across two takeoffs, the orthomosaic processing may produce two separate GeoTIFFs. Merge them into one file for client delivery.
Re-assemble downloaded basemap tiles
Some basemap providers deliver imagery as a set of pre-georeferenced tiles. Merge them once locally rather than re-downloading every time.
Combine masked outputs
If you ran several mask operations across different regions of the same dataset, merge the per-region results into a single output for downstream analysis.
Build a custom raster pyramid input
Some pipelines (raster servers, web tile generators) expect a single source GeoTIFF. Merge first, then feed the combined output into your pyramid build.
Compatibility checklist
All input GeoTIFFs must match on each of these properties. The tool checks automatically and shows which property doesn't match if validation fails.
| Property | Must match? | If they don't |
|---|---|---|
| CRS (EPSG code) | Yes | Reproject one with /reproject-geotiff first. |
| Pixel resolution | Yes | Resample one with /resample-raster to match. |
| Number of bands | Yes | Use /extract-band to take matching bands from each. |
| Bit depth + sample format | Yes | Convert inputs to a common bit depth in QGIS or rasterio. |
| Tile alignment | Not strictly | The mosaic snaps to the first input's pixel grid. Off-grid inputs may land with sub-pixel offsets. |
How the merge works
- Inspect. Each input is opened with geotiff.js and its georeferencing — origin, resolution, CRS, sample count, bit depth — is read from the file header.
- Validate. All inputs must share CRS, resolution, sample count, and bit depth. Mismatches are surfaced before any pixel data is read.
- Compute union extent. The tool calculates the minimum axis-aligned rectangle in the shared CRS that contains every input's footprint.
- Allocate output buffer. A single typed-array buffer sized to the union dimensions, with the same band count and bit depth as the inputs.
- Copy pixel blocks. Each input's raster bytes are copied into the right offset of the output buffer. Last-wins on overlap.
- Write the GeoTIFF. The output is encoded via geotiff.js with the union extent and the inputs' CRS, and downloaded directly to your machine.
Privacy and architecture
All file inspection, validation, and merging happens in your browser using JavaScript and the geotiff.js library. No files are uploaded to QuickMapTools servers. The tool requires a Pro subscription so the engineering effort to build and maintain it is supported by paying users — but the data path itself is identical to our free tools.
Frequently asked questions
How do I merge multiple GeoTIFFs into one file?
Drop two or more .tif files onto the tool above. The tool inspects each file, confirms they share the same CRS, resolution, band count, and bit depth, then writes a single mosaic GeoTIFF covering the union of their extents. Everything runs in your browser — files never leave your device.
What kind of GeoTIFFs can I merge?
Any GeoTIFFs that share the same CRS (EPSG code), the same pixel resolution, the same number of bands, and the same bit depth. This includes Sentinel-2 scene clips from adjacent UTM tiles, Landsat clips from neighbouring scenes, DEM tiles from the same source, and adjacent drone orthomosaics rendered against a common reference.
My files have different CRSes — can I still merge them?
No — reproject one of them first using our Reproject GeoTIFF tool so all inputs share an EPSG code, then merge. Auto-reprojection inside the merge tool would hide important precision decisions, so we keep the steps explicit.
What about different resolutions or different bit depths?
The same rule applies — resample inputs to a common resolution and convert to a common bit depth before merging. The tool detects mismatches and tells you which inputs differ and how.
How does the tool handle overlapping pixels?
Last file wins. If two inputs cover the same pixel, the later one in the file list overwrites the earlier one. For mosaicking adjacent satellite scene clips this rarely matters because overlaps are minimal — but if it matters for your data, reorder the file list before merging.
How large can the output be?
The tool runs in browser memory, so the practical limit depends on your machine. As a rough rule, mosaics up to a few hundred megapixels per band work fine on modern laptops. The output uses the same bit depth as the inputs.
Does this tool reproject or resample?
No. The merge is a pure pixel-copy operation: it reads each input's rasters, writes them into the right position of a larger output grid, and saves the result. Inputs must already be aligned. This is intentional — reprojection and resampling are separate, explicit steps with their own tools on QuickMapTools.
Is the output GeoTIFF compressed?
The output uses the same byte layout the inputs use, written via geotiff.js. For most use cases the file opens directly in QGIS, ArcGIS, rasterio, and any GDAL-aware viewer. If you need DEFLATE compression for archival you can re-save the output through a desktop GIS or run it through gdal_translate offline.