The lz4 algorithm is also tiny code-wise. Pulling in a lz4 compressor / decompressor library into my wasm project only added 11kb to the bundled size. Zstd is many times larger.

For my use case, any extra benefits of zstd are far outweighed by the extra cost of downloading zstd itself in the browser.

LZ4 is smaller, faster and much more simple.