Change Log

August 20, 2026 ยท View on GitHub

All notable changes to this project will be documented in this file. This project adheres to Semantic Versioning.

The public API of this library consists of the functions declared in file h3api.h.in.

[Unreleased]

Fixed

  • Fixed the polygonToCells fuzzer regression test to use explicit double literals instead of reinterpreting raw bytes, so it is portable across endianness (#964)
  • No longer emit a CMake warning about a missing clang-format/clang-tidy when the user explicitly set ENABLE_FORMAT=OFF/ENABLE_LINTING=OFF (#1158)
  • Fixed an out of bounds read in _baseCellToCCWrot60 when passed a face index equal to NUM_ICOSA_FACES (#978)

[4.5.0] - 2026-05-21

Added

  • cellsToMultiPolygon function (#1104, #1113)
    • Internal for now, will be added to the public API in a future release
    • destroyGeoMultiPolygon function (#1104)
    • (internal) geoLoopArea function (#1101)
  • reverseDirectedEdge function (#1098)
  • Bidirectional gridPathCells (#1111)
  • h3.pc pkg-config file (#1115)

Changed

  • cellsToLinkedMultiPolygon now uses cellsToMultiPolygon internally (#1126, #1133, #1136)
    • cellsToLinkedMultiPolygon (and cellsToMultiPolygon) now return errors for invalid cells (E_CELL_INVALID), mixed resolutions (E_RES_MISMATCH), and duplicate cells (E_DOMAIN) instead of producing undefined output
  • cellAreaRads2 uses geoLoopArea (#1101)
  • Refactor of indexing code to use Vec3d (#1145, #1155)
  • Refactor of CoordIJK code to be inlineable (#1154)

Fixed

  • CLI handling of invalid cell input (#1125, #1124)
  • destroyLinkedMultiPolygon is now idempotent (safe to call twice) (#1136)

[4.4.1] - 2025-11-11

Fixed

  • Proper version set in VERSION file (#1091)

[4.4.0] - 2025-11-06

Added

  • getIndexDigit function for inspecting specific index digits of an H3 index. (#1024, #1042)
  • isValidIndex function (#1056, #1079)
  • constructCell function (#1063, #1074, #1078)
  • New H3_INDEX_INVALID, E_BASE_CELL_DOMAIN, E_DIGIT_DOMAIN, E_DELETED_DIGIT error codes and H3_ERROR_END (#1063, #1064, #1065)

Changed

  • Updated minimum version of macOS in CI. (#1069)

[4.3.0] - 2025-06-17

Added

  • Added gridRing function, that works even if encountering pentagon distortion. (#1011, #1013, #1015)

[4.2.1] - 2025-03-10

Fixed

  • Fixed MSVC/WIN32 checks in CMake. (#981)
  • Fixed potential memory leak in polygonStringToGeoPolygon (#976)

Changed

  • Added arm64 tests in CI. (#975, #974)
  • Faster isValidCell (#968)
  • Moved ContainmentMode enum for polygonToCellsExperimental to h3api.h. (#958)

[4.2.0] - 2024-12-04

Added

  • Added experimental new algorithm for polygonToCells, called polygonToCellsExperimental, that supports more containment flags and is more memory-efficient (#785, #800, #947)
  • h3 binary for shell scripts ready for use (#818, #826, #846, #923, #924, #931, #933)

Fixed

  • Fixed compacting all or many resolution 1 cells (#919)

Changed

  • compactCells internally uses int64 for array indexing. (#920)
  • Reorganize tests into public / internal. (#762)
  • Performance enhancement for aarch64, may improve other platforms (#790, #792, #852, #905, #913)
  • clang-format upgraded to version 14. (#834)
  • Fixed tests that incorrectly did not test resolution 15. (#820)
  • Use CMAKE_INSTALL_LIBDIR when choosing where to install library files. (#819)

[4.1.0] - 2023-01-18

Added

  • Functions for cellToChildPos and childPosToCell (#719)

Fixed

  • Fixed possible signed integer overflow in h3NeighborRotations (#707)
  • Fixed possible signed integer overflow in localIjToCell (#706, #735)

Changed

  • assert on defensive code blocks that are not already covered. (#720)
  • clang-format upgraded to version 11. (#734)

[4.0.1] - 2022-09-15

Fixed

  • Changing an internal float to double improves the precision of geographic coordinate output (#652)
  • Fixed compacting all children of a resolution 0 cell (#679)
  • Fixed possible signed integer overflow in maxGridDiskSize (#686)
  • Fixed possible use of uninitialized values in cellToVertex (#683, #690)
  • Fixed possible out of bounds read in localIjToCell (#684)
  • Fixed possible memory leak in compactCells (#685)
  • Fixed possible out of bounds read in areNeighborCells (#677)
  • Fixed possible memory leak in cellsToLinkedMultiPolygon (#673)

Changed

  • Build script does not use toolchain file (#641)
  • Removed a duplicated include preprocessor directive (#682)
  • Improvements to the fuzzer suite and their automatic runs in CI (#671, #674, #687)
  • Increased test coverage (#642)
  • Added a fuzzer targeting internal algos.c functions (#675)

[4.0.0] - 2022-08-23

Breaking changes

  • Rename functions according to the terminology RFC (#622, #586, #571, #403, #466, #495, #466)
  • Functions that can experience errors now have an H3Error return value. (#617, #586, #581, #551, #550, #509, #505, #507, #508, #503, #478, #468, #436, #359)
  • Cell count parameters use int64_t instead of int.
  • polygonToCells (previously polyfill) accepts a flags argument for future expansion. (#570)
  • cellToLocalIj and localIjToCell accept a mode argument for future expansion. (#586)
  • exactEdgeLength functions renamed to edgeLength (#639)

Fixed

  • Fix polyfill bug when vertex latitude exactly matches cell center. (#603)
  • A number of issues detected via unit tests and fuzzers were fixed. (#568, #562, #558, #559, #560, #430)
  • polygonToCells returns an error if Infinity is passed in. (#636)

Changed

  • The file CMakeTests.cmake is no longer included if ENABLE_TESTING is off. (#609)

Added

  • Vertex mode and associated functions: (#422, #420, #417)
    • cellToVertex(cell, vertexNum)
    • cellToVertexes(cell, out)
    • vertexToLatLng(vertex, out)
    • isValidVertex(vertex)
  • h3 CLI application. (#556, #497)

Other changes

  • Generally use lng instead of lon
  • Closed-form implementation of numHexagons
  • A number of fuzzer harnesses are now included in the H3 core library. (#557, #553, #545, #433)
  • Additional benchmarks are added and benchmarks are regularly run in CI. (#524, #518)

[4.0.0-rc5] - 2022-08-16

Breaking changes

  • exactEdgeLength functions renamed to edgeLength (#639)

Fixed

  • polygonToCells returns an error if Infinity is passed in. (#636)

[4.0.0-rc4] - 2022-07-25

Breaking changes

  • distance* functions (distanceKm, etc) renamed to greatCircleDistance*. (#622)
  • Error code E_MEMORY renamed to E_MEMORY_ALLOC. (#617)

[4.0.0-rc3] - 2022-06-03

Fixed

  • Fix polyfill bug when vertex latitude exactly matches cell center. (#603)

Changed

  • The file CMakeTests.cmake is no longer included if ENABLE_TESTING is off. (#609)

[4.0.0-rc2] - 2022-03-16

Breaking changes

  • experimentalH3ToLocalIj and experimentalLocalIjToH3 renamed to cellToLocalIj and localIjToCell respectively. (#586)
  • cellToLocalIj and localIjToCell accept a mode argument for future expansion. (#586)
  • cellToCenterChild (previously h3ToCenterChild) returns an error code. (#581)

Added

  • E_OPTION_INVALID error code added. (#586)

[4.0.0-rc1] - 2022-02-07

Breaking changes

  • Rename functions according to the terminology RFC (#571, #403, #466, #495, #466)
  • Functions that can experience errors now have an H3Error return value. (#551, #550, #509, #505, #507, #508, #503, #478, #468, #436, #359)
  • Cell count parameters use int64_t instead of int.
  • polygonToCells (previously polyfill) accepts a flags argument for future expansion. (#570)

Added

  • Vertex mode and associated functions: (#422, #420, #417)
    • cellToVertex(cell, vertexNum)
    • cellToVertexes(cell, out)
    • vertexToLatLng(vertex, out)
    • isValidVertex(vertex)
  • h3 CLI application. (#556, #497)

Fixed

  • A number of issues detected via unit tests and fuzzers were fixed. (#568, #562, #558, #559, #560, #430)

Other changes

  • Generally use lng instead of lon
  • Closed-form implementation of numHexagons
  • A number of fuzzer harnesses are now included in the H3 core library. (#557, #553, #545, #433)
  • Additional benchmarks are added and benchmarks are regularly run in CI. (#524, #518)

[3.7.2] - 2021-07-15

Fixed

  • gridDisk of invalid indexes should not crash. (#498)

[3.7.1] - 2020-10-05

Fixed

  • Finding invalid edge boundaries should not crash. (#399)
  • Build fixes for FreeBSD. (#397)

[3.7.0] - 2020-09-28

Added

  • Area and haversine distance functions (#377):
    • cellAreaRads2
    • cellAreaKm2
    • cellAreaM2
    • pointDistRads
    • pointDistKm
    • pointDistM
    • exactEdgeLengthRads
    • exactEdgeLengthKm
    • exactEdgeLengthM
  • Refactor getH3UnidirectionalEdgeBoundary for accuracy at small resolutions. (#391)
    • Speeds up getH3UnidirectionalEdgeBoundary by about 3x.
    • Implement core logic for future vertex mode.

Fixed

  • Fixed building the library with custom memory allocation functions on Mac OSX. (#362)
  • The installed H3 CMake target should have include directories specified. (#381)

Changed

  • Tests now use bash on Windows. (#381)

[3.6.4] - 2020-06-19

Added

  • H3_MEMORY_PREFIX CMake option for replacing the memory management functions used in H3. (#317)
  • Support for building Debian packages of H3. (#352)

Fixed

  • Removed duplicate include statements. (#333)
  • Fixed macro H3_DIGIT_MASK_NEGATIVE. (#329)

Changed

  • Again implement new polyfill algorithm. (#313)

[3.6.3] - 2020-01-21

Fixed

  • compact detects and fails on cases with duplicated input indexes. (#299)

Changed

  • h3IsValid returns false for indexes that have non-zero reserved bits. (#300)
  • h3IsValid and h3UnidirectionalEdgeIsValid return false for indexes with the high bit set. (#300)

[3.6.2] - 2019-12-9

  • Revert new polyfill algorithm until reported issues are fixed. (#293)

[3.6.1] - 2019-11-11

Fixed

  • compact handles zero length input correctly. (#278)
  • bboxHexRadius scaling factor adjusted to guarantee containment for polyfill. (#279)
  • polyfill new algorithm for up to 3x perf boost. (#282)
  • Fix CMake targets for KML generation. (#285)

[3.6.0] - 2019-08-12

Added

  • h3ToCenterChild function to find center child at given resolution (#267)
  • getPentagonIndexes (and pentagonIndexCount) function to find pentagons at given resolution (#267)

Fixed

  • Fix bounds check for local IJ coordinates (#271)

[3.5.0] - 2019-07-22

Added

  • CMake options for excluding filter applications or benchmarks from the build. (#247)
  • h3GetFaces function to find icosahedron faces for an index, and helper function maxFaceCount (#253)

Changed

  • Argument parsing for all filter applications is more flexible. (#238)

Fixed

  • Fix printing program name in h3ToHier error messages. (#254)

[3.4.4] - 2019-05-30

Changed

  • Local coordinate spaces cannot cross more than one icosahedron edge. (#234)
  • All dynamic internal memory allocations happen on the heap instead of the stack. (#235)
  • Argument parsing for h3ToGeo, geoToH3, and h3ToGeoBoundary is more flexible. (#227)

[3.4.3] - 2019-05-02

Added

  • localIjToH3 filter application (#222)
  • An option to print distances in the kRing filter application (#222)

Changed

  • Arguments parsing for kRing filter application is more flexible. (#224)

Fixed

  • benchmarkPolyfill allocates its memory on the heap (#198)
  • Fixed constraints of vertex longitudes (#213)
  • Zero only input to uncompact does not produce an error (#223)

[3.4.2] - 2019-02-21

Changed

  • binding-functions build target generates an ASCII file on Windows (#193)

[3.4.1] - 2019-02-15

Fixed

  • binding-functions build target fixed when running the build out of source (#188)

[3.4.0] - 2019-01-23

Added

  • getRes0Indexes function for getting all base cells, and helper function res0IndexCount (#174)
  • Include defined constants for current library version (#173)

[3.3.0] - 2018-12-25

Added

  • h3Line and h3LineSize functions for getting the line of indexes between some start and end (inclusive) (#165)

Changed

  • Indexes in deleted pentagon subsequences are not considered valid.

[3.2.0] - 2018-10-04

Added

  • experimentalH3ToLocalIj function for getting local coordinates for an index. (#102)
  • experimentalLocalIjToH3 function for getting an index from local coordinates. (#102)
  • Benchmarks for the kRing method for k's of size 10, 20, 30, and 40. (#142, #144)

Changed

  • Internal h3ToIjk function renamed to h3ToLocalIjk. (#102)
  • h3ToIjk filter application replaced with h3ToLocalIj. (#102)

Fixed

  • Added #include <stdio.h> to benchmark.h (#142)

[3.1.1] - 2018-08-29

Fixed

  • Fixed bounding box bug for polygons crossing the antimeridian (#130)
  • Normalize output of h3SetToMultiPolygon to align with the GeoJSON spec, ensuring that each polygon has only one outer loop, followed by holes (#131)

Changed

  • Longitude outputs are now guaranteed to be in the range [-Pi, Pi]. (#93)
  • Implemented closed form formula for maxKringSize. Source: https://oeis.org/A003215 (#138)
  • Improved test and benchmark harnesses (#126, #128)

[3.1.0] - 2018-08-03

Added

  • h3Distance function for determining the grid distance between H3 indexes (#83)
  • Internal h3ToIjk function for getting IJK+ coordinates from an index (#83)
  • Internal ijkDistance function for determining the grid distance between IJK+ coordinates (#83)
  • h3ToIjk filter application for experimenting with h3ToIjk (#83)

Fixed

  • Don't require a C++ compiler (#107)

Changed

  • Most dynamic internal memory allocations happen on the heap instead of the stack (#100)

[3.0.8] - 2018-07-18

Added

  • Added Direction enum, replacing int and defined constants (#77)

Fixed

  • Ensured unused memory is cleared for pentagon children. (#84)
  • Fixed compiler warnings in h3ToGeoHier and h3ToGeoBoundaryHier. (#90)
  • Fixed a segfault in h3SetToLinkedGeo (#94)

Changed

  • Warnings are not errors by default. (#90)

[3.0.7] - 2018-06-08

Added

  • Generator for the faceCenterPoint table (#67)
  • Generator for number of indexes per resolution (#69)
  • Added CMake WARNINGS_AS_ERRORS option, default on, for Clang and GCC (#70)
  • Added CMake TEST_WRAPPER setting when WRAP_VALGRIND is on (#66)

Changed

  • Moved Vec3d structure to vec3d.h (#67)
  • Added input validation when getting the origin or destination of an edge (#74)

[3.0.6] - 2018-06-01

Changed

  • Changed signature of internal function h3NeighborRotations.
  • Do not require support for hexRange, hexRanges, or hexRangeDistances in the bindings. These functions may be deprecated in the public API in future releases; consumers should use kRing and kRingDistances instead.
  • Performance improvement in core indexing logic for geoToH3 (thanks @wewei!)

[3.0.5] - 2018-04-27

Fixed

  • Fixed duplicate vertex in h3ToGeoBoundary for certain class III hexagons (#46)

Added

  • Release guide

[3.0.4] - 2018-04-16

Added

  • Assertions when allocating memory on the heap.

Changed

  • Most internal memory allocations happen on the stack instead of the heap.

[3.0.3] - 2018-03-19

Added

  • CMake config installation to ease use of h3 from CMake projects.
  • Add CMake toolchain file to set build options upfront.
  • Add CMake C_CLANG_TIDY property to integrate clang-tidy checks during build.
  • YouCompleteMe completion support.

Changed

  • Improved resilience to out of range inputs.
  • Minimum CMake version to 3.1.
  • Set CMAKE_C_STANDARD to 11 instead of using compiler flag -std=c1x.
  • Use CMAKE_POSITION_INDEPENDENT_CODE instead of using compiler flag -fPIC.
  • Rename library target from h3.1 to h3 with SONAME property of 1.

Removed

  • CMake H3_COMPILER option in favor of built-in CMAKE_C_COMPILER.
  • CMake BUILD_STATIC option in favor of built-in BUILD_SHARED_LIBS.
  • CMake ENABLE_TESTS option in favor of built-in BUILD_TESTING.
  • File globbing in CMake in favor of listing source files.

[3.0.2] - 2018-01-24

Removed

  • Removed the H3IndexFat internal structure.

Changed

  • Simplified build process on Windows.

Fixed

  • Fixed an issue where tests would fail on ARM systems.

[3.0.1] - 2018-01-18

Added

  • Added a make install target.

Changed

  • Improved compatibility with building on Windows.
  • Fixed various cases where the test suite could crash or not compile.

[3.0.0] - 2018-01-08

Added

  • First public release.