Dependencies

DuckDB has no required runtime dependencies outside the C++17 standard library. Everything else is vendored as source under third_party/. This makes the engine easy to embed and easy to build for unusual targets (Wasm, Android, embedded systems).

Vendored libraries

Directory	Library	Purpose
third_party/brotli/	Brotli	Optional compression codec for parquet writes.
third_party/catch/	Catch2	Test framework for the C++ test suite.
third_party/concurrentqueue/	moodycamel::ConcurrentQueue	Lock-free queue used in the task scheduler.
third_party/fast_float/	fast_float	Fast string-to-float parsing used by the CSV scanner.
third_party/fastpforlib/	FastPFOR	Bit-packed integer compression used by parquet.
third_party/fmt/	fmt	Formatting library used in error messages.
third_party/fsst/	FSST	String compression (DuckDB-developed).
third_party/httplib/	cpp-httplib	Used by extensions only (httpfs); engine itself does not depend on HTTP.
third_party/hyperloglog/	HyperLogLog	Approximate distinct counting.
third_party/imdb/	IMDb data	Test fixtures for join-order benchmarks.
third_party/jaro_winkler/	jaro-winkler	Implementation of the jaro_winkler similarity function.
third_party/lz4/	LZ4	Compression codec; used by parquet's LZ4_RAW.
third_party/mbedtls/	mbed TLS	Crypto primitives (AES, hashes, X.509).
third_party/miniz/	miniz	Minimal zlib/deflate implementation; used for gzip-compressed inputs.
third_party/parquet/	Apache Parquet C++ headers	Thrift schema for parquet metadata.
third_party/pcg/	PCG	Pseudo-random number generator.
third_party/pdqsort/	pdqsort	Pattern-defeating quicksort used internally.
third_party/re2/	RE2	Regex engine used by regexp_* functions.
third_party/ska_sort/	ska_sort	Radix sort variant.
third_party/skiplist/	skip list	Used in the optimizer/window code.
third_party/snappy/	Snappy	Compression codec for parquet.
third_party/snowball/	Snowball stemmer	Optional FTS support.
third_party/tdigest/	t-digest	Approximate quantiles.
third_party/thrift/	Apache Thrift	Subset for parquet metadata serialization.
third_party/utf8proc/	utf8proc	UTF-8 normalization and case folding.
third_party/vergesort/	vergesort	Adaptive sort variant.
third_party/yyjson/	yyjson	Fast JSON parser used by the JSON extension.
third_party/zstd/	Zstandard	General-purpose compression; used in many places.
third_party/pegtl/	PEGTL	PEG parser combinator framework powering the SQL grammar.

PEGTL is at third_party/pegtl/ and is the engine for src/parser/peg/.

Optional (extension-only) dependencies

These are pulled in only when the relevant extension is built:

Extension	External source	Notes
parquet	none extra (Thrift + Snappy + ZSTD vendored)	Built-in.
json	yyjson (vendored)	Built-in.
icu	Vendored ICU subset (extension/icu/third_party/)	Replaces system ICU.
delta	delta-kernel-rs (Rust)	Fetched at build time; requires Rust.
tpch / tpcds	Vendored dbgen / dsdgen	Built-in.
httpfs (out-of-tree)	mbedtls + cpp-httplib	Out-of-tree; pulls from this repo's vendored libs.
aws (out-of-tree)	aws-sdk-cpp	Out-of-tree.
iceberg (out-of-tree)	Avro + JSON	Out-of-tree.

Build-time dependencies

Tool	Required for
C++17 compiler (GCC 7+, Clang 6+, MSVC 2019+)	Building the engine.
CMake 3.5+	Configuring the build.
Python 3	Code generation scripts in scripts/, the test runner.
Optional: clang-format 11.0.1	make format-fix.
Optional: black	make format-fix (Python).
Optional: ninja	Faster builds with GEN=ninja make.
Optional: ccache	Auto-detected for faster rebuilds.
Optional: Rust toolchain	Building the delta extension.

The amalgamation build (scripts/amalgamation.py) produces a single duckdb.cpp plus header that has only the C++ standard library as a dependency — used for embedding in environments where pulling in CMake is impractical.

Vendoring policy

DuckDB vendors third-party dependencies on principle. The reasons:

• Determinism. A given commit always builds the same way, regardless of system libraries.
• Portability. WASM, Android, and minimal Linux containers do not always ship system libraries.
• Single-binary embedding. The amalgamation build produces a .cpp file with no other dependencies.

When updating a vendored library, the workflow is in scripts/ (e.g., extension/icu/scripts/ for ICU updates). Patches are applied as part of the import.

Where to look

• The vendor list in any one place: third_party/ (this directory).
• Per-extension vendored sources: extension/<name>/third_party/ (e.g., extension/icu/third_party/).
• License notices: each third_party/<name>/LICENSE (or equivalent).