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Top 23 C++ API Projects
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I've been vibe coding some music tools and after some researching let Claude get going with imgui (https://github.com/ocornut/imgui) to build a tool I use for local authoring. It's pretty pixel-dense and looks alright to me. It runs on MacOS and Linux, which is enough for my needs now. Claude has been pretty decent at getting audio stuff going on MacOS and can even tap into various accelerators in MacOS libraries. It's had no problems loading and playing mp3s and m4as, which is the majority of my collection. I'll probably prototype an music manager off of that. It'd be great if it works out for Android as well.
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Zeal (open source, free) is a free/libre/open source docset viewer that runs on Windows, Linux, and BSD. While it is possible to build Zeal for MacOS, the recommendation is to download Dash.
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manticoresearch
Easy to use open source fast database for search | Good alternative to Elasticsearch | Drop-in replacement for E in the ELK stack
Search Engine: Manticore Search (running in Docker). We chose Manticore for its lightweight footprint and powerful full-text search capabilities, essential for RAG (Retrieval-Augmented Generation).
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glaze
Extremely fast, in memory, serialization, reflection, and RPC library for C++. JSON, BEVE, BSON, CBOR, CSV, JSONB, MessagePack, TOML, YAML, EETF
Project mention: Glaze: Fast JSON with built-in HTTP Server for modern C++ | news.ycombinator.com | 2025-09-09 -
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ccapi
A header-only C++ library for interacting with crypto exchanges. Bindings for Python, Java, C#, Go, and Javascript are provided.
I work for a medium-sized proprietary/discretionary fund. AFAIK the principles trade all kinds of stuff, macro stuff. My current job is tuning up the execution on the cryptocurrency adjacent desk, but not like blockchain stuff, it's somewhere in between OG crypto trading stuff and like Wall St. HFT circa 2006-2010 depending on how you measure, it's in the "kernel bypass matters but FPGAs are still exotic" sort of regime, some of it is legacy REST APIs still but FIX 4.2 SBE and other real finance protocols (and real banks and stuff) are starting to be a part of the ecosystem.
I aspire to be a lot faster than this stuff (I've built faster stuff than this) but this is quite a good library (amazingly good by OSS standards, good stuff in this area is rarely OSS, props to the maintainers): https://github.com/crypto-chassis/ccapi, in particular this library does a really good job of being correct across a lot of surface area, it's serious people doing it, and there are forks of it that use DPDK floating around.
If by who's paying for it you mean the big Anthropic bill? My boss's boss is pretty enlightened about the fact that learning how to use AI well is expensive, so when I'm on a tight schedule I get a pretty forgiving budget for the model fees. It's a pretty serious perk in the sense that it's really expensive to master using these things :)
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TOSDataBridge
A collection of resources for pulling real-time streaming data off of TDAmeritrade's ThinkOrSwim(TOS) platform; providing C, C++, Java and Python interfaces.
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Here's the concrete example that started it. The upstream ArduinoCore-API Print class gives you print() and println(), but no printf(). Tons of firmware (MeshCore included) calls Serial.printf(...). Upstream hasn't added it. So you have to shim it in somewhere.
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For pure duckdb, you can put an Arrow Flight server in front of duckdb[0] or use the httpserver extension. Where you store the .duckdb file will make a big difference in performance (e.g. S3 vs. Elastic File System).
But I'd take a good look at ducklake as a better multiplayer option. If you store `.parquet` files in blob storage, it will be slower than `.duckdb` on EFS, but if you have largish data, EFS gets expensive.
We[2] use DuckLake in our product and we've found a few ways to mitigate the performance hit. For example, we write all data into ducklake in blog storage, then create analytics tables and store them on faster storage (e.g. GCP Filestore). You can have multiple storage methods in the same DuckLake catalog, so this works nicely.
0 - https://www.definite.app/blog/duck-takes-flight
1 - https://github.com/Query-farm/httpserver
2 - https://www.definite.app/
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docwire
DocWire SDK: Award-winning modern data processing in C++20. SourceForge Community Choice & Microsoft support. AI-driven processing. Supports nearly 100 data formats, including email boxes and OCR. Boost efficiency in text extraction, web data extraction, data mining, document analysis. Offline processing is possible for security and confidentiality
Project mention: DocWire SDK 2025.06.19 Released – Major OCR & PDF Layout Upgrades, Archive Refactor, CI Improvements | dev.to | 2025-06-25Full release notes: https://github.com/docwire/docwire/releases/tag/2025.06.19
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NOTE:
The open source projects on this list are ordered by number of github stars.
The number of mentions indicates repo mentiontions in the last 12 Months or
since we started tracking (Dec 2020).
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A note from our sponsor - SaaSHub
www.saashub.com | 10 Jun 2026
Index
What are some of the best open-source API projects in C++? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | imgui | 73,701 |
| 2 | zeal | 12,653 |
| 3 | manticoresearch | 11,819 |
| 4 | glaze | 2,835 |
| 5 | xlnt | 1,637 |
| 6 | DPP | 1,360 |
| 7 | opentelemetry-cpp | 1,292 |
| 8 | oneMath | 764 |
| 9 | Stim | 742 |
| 10 | ola | 734 |
| 11 | ccapi | 724 |
| 12 | hwinfo | 702 |
| 13 | imgui_test_engine | 586 |
| 14 | DualSense-Windows | 436 |
| 15 | TOSDataBridge | 337 |
| 16 | ArduinoCore-API | 297 |
| 17 | BakkesModSDK | 281 |
| 18 | httpserver | 279 |
| 19 | roq-cpp-samples | 167 |
| 20 | Fwog | 158 |
| 21 | Chata | 112 |
| 22 | docwire | 108 |
| 23 | BakkesMod2-Plugins | 99 |
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