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WebPublish can compress HTTP responses using gzip or deflate before sending them to the client. Compression is configured per task — you can enable it for one task and disable it for another depending on the content type.

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How it works

When a client sends an Accept-Encoding: gzip header, WebPublish checks the task’s gzip setting:
  • Gzip enabled — the response body is compressed with zlib.gzipSync before it is sent. If the client instead advertises Accept-Encoding: deflate, zlib.deflateSync is used.
  • Gzip disabled — the response is sent uncompressed, regardless of what the client accepts.
The Content-Encoding response header is set to gzip or deflate so the client knows to decompress the body.

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Enabling and disabling gzip

Gzip is a per-task setting. It defaults to true for all task types. To change it, open the task’s edit dialog:
1

Open the task settings

Click the task in the publish list, then click Edit (or the pencil icon).
2

Toggle gzip

Find the Gzip toggle and switch it on or off.
3

Save the task

Click OK (or Save & Apply). The change takes effect immediately — no server restart is required.

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When to enable gzip

Gzip is beneficial for content that compresses well and is not already compressed at the storage level.
Content typeRecommended settingReason
Static HTML, CSS, JSEnabledText compresses well; reduces transfer size significantly
GeoJSONEnabledJSON is highly compressible
Large JSON or XML filesEnabledReduces bandwidth for large structured data
PNG raster tilesDisabledPNG is already losslessly compressed; re-compressing adds CPU cost with negligible size reduction
Video, audio, JPEG imagesDisabledAlready compressed; gzip overhead is not worth the marginal gain
When in doubt, leave gzip enabled. WebPublish only compresses when the client advertises support, so enabling gzip never breaks clients that do not understand it.

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MBTiles vector tiles: special handling

MBTiles files that store vector tiles in PBF format often compress the tile data internally with gzip before writing it to the SQLite database. WebPublish detects this at request time by checking for the gzip magic bytes (0x1f 0x8b) at the start of the tile buffer. The result depends on whether the stored tile is already compressed and whether the client accepts gzip:
Stored tileClient accepts gzipTask gzip settingWhat WebPublish sends
Already gzip-compressedYesEnabledPasses the compressed tile through unchanged
Already gzip-compressedNoEnabledDecompresses the tile before sending
Not compressedYesEnabledCompresses the tile before sending
Not compressedNoDisabledSends the tile uncompressed
This means you can safely leave gzip enabled on MBTiles tasks regardless of how tiles are stored in the file — WebPublish handles passthrough and decompression transparently.
The gzip passthrough path is the most efficient: if the stored tile is already compressed and the client accepts gzip, no CPU work is done on the tile data at all.

MBTiles task

Full reference for the MBTiles tile server task type

File task

Serve individual files with optional gzip compression

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