LinuxWhat is the BIL file format?
A .bil file stores raw binary raster image data organized in band-interleaved-by-line (BIL) pixel order. The format was standardized by ESRI for ArcView in the early 1990s, with roots in 1980s satellite remote sensing data distribution.
A .bil file is not self-describing - it requires a companion .hdr file with the same base name. The .hdr is a plain ASCII keyword-value file that specifies dimensions (NROWS, NCOLS), band count (NBANDS), bit depth (NBITS), and byte order (BYTEORDER I for little-endian or M for big-endian). Optional sidecar files round out a complete BIL dataset:
.prj- coordinate system (WKT projection).blw/.bpw- world file for georeferencing.clr- color map for palette-mapped data.sta- band statistics
The interleaving order writes all bands for a given row before advancing: [R1-Band1][R1-Band2][R1-Band3][R2-Band1]... This is a middle ground between .bsq (band sequential, fast for single-band reads) and .bip (band interleaved by pixel, fast for multi-band pixel access).
The USGS distributes the National Land Cover Database (NLCD) and some DEMs as BIL. Modern workflows favor GeoTIFF or Cloud Optimized GeoTIFF, but BIL remains supported in QGIS, ArcGIS Pro, and GDAL (gdal_translate). The .bil file is useless without its matching .hdr - always keep them together.
Security & safety
RISK: LOWBIL is a passive raw data format with no scripting capability. The .hdr companion file is plain text and cannot execute code. Safe to open in any GIS application. Extremely large files may cause memory issues if opened without appropriate GIS software.
Format details
in a nutshell- Band Interleaved by Pixel (BIP) - sometimes shares .bil extension incorrectly - BIP is a related interleaving format; a mislabeled or misexported file may have the wrong extension. The .hdr LAYOUT keyword distinguishes them.
Programs that open BIL files
Windows5 apps
Global Mapper
Paid File → Open Data File(s); select .bil. Supports BIL with all sidecar files automatically. 
Total GIS Converter
Paid Batch conversion of BIL files to GeoTIFF, PNG, JPG, and other raster formats. 
QGIS
Open-source Layer → Add Layer → Add Raster Layer; select .bil file. QGIS (via GDAL) reads it automatically if .hdr is present.
ArcGIS Pro
Paid Add Data → navigate to .bil file; ESRI natively supports BIL including ArcView legacy files.
GDAL (gdal_translate)
Open-source gdal_translate input.bil output.tif - reads BIL and converts to GeoTIFF or any GDAL-supported format. 
macOS1 app
Technical details
deep spec| Pixel interleave order | Band-by-band per row: all bands for row N written before row N+1 |
| Required companion file | .hdr ASCII keyword-value file (NROWS, NCOLS, NBANDS, NBITS, BYTEORDER) |
| Byte order | Configurable via .hdr: I = little-endian (Intel), M = big-endian (Motorola) |
| Bit depth | 1-64 bits per band per pixel as specified in NBITS; commonly 8-bit or 16-bit |
| Compression | None (uncompressed raw binary) |
| Georeferencing | Optional .blw/.bpw world file; optional .prj projection WKT sidecar |
| Color map sidecar | .clr file for palette-mapped datasets |
| Band statistics sidecar | .sta file for precomputed band statistics |
| Typical file size | 1 MB - several GB depending on dimensions, band count, and bit depth |
| Format versioning | None; format defined entirely by .hdr keyword-value pairs |
| GDAL driver | EHdr driver; read/write support via gdal_translate |
| USGS distribution use | National Land Cover Database (NLCD) and some DEM products distributed as BIL |
| Relation to BIP / BSQ | Same .hdr format as .bip and .bsq; only the pixel interleaving order differs |
| Dimension limits | No inherent format limit; GDAL supports up to 2^31 rows/columns |
| Released | circa 1980s (remote sensing industry); popularized by ESRI ArcView in early 1990s |
| Latest version | No version; format is stable and unchanged |
| Open standard | Yes · royalty-free |
| Specification | desktop.arcgis.com |
BIL conversions
Community Q&A
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