LLM Serialization Formats LLM Tools

Data serialization formats specifically optimized to reduce token consumption in LLM contexts while maintaining human readability. Includes format specifications, converters, and implementations. Does NOT include general-purpose serialization (Protocol Buffers, MessagePack), compression algorithms unrelated to LLM optimization, or data storage systems.

There are 39 llm serialization formats tools tracked. 4 score above 50 (established tier). The highest-rated is toon-format/toon at 67/100 with 23,207 stars. 1 of the top 10 are actively maintained.

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#	Tool	Score	Tier	Stars	Language
1	toon-format/toon 🎒 Token-Oriented Object Notation (TOON) – Compact, human-readable,...	67	Established	23,207	TypeScript
2	dweve-ai/hedl Token-efficient data serialization for LLM/AI. 50% fewer tokens than JSON,...	55	Established	65	Rust
3	tonl-dev/tonl TONL (Token-Optimized Notation Language)	54	Established	826	TypeScript
4	toon-format/toon-java ☕ Community-driven Java implementation of TOON	52	Established	140	Java
5	ISON-format/ison 🔥 🔥 Alternative to JSON 🔥 🔥	43	Emerging	126	Python
6	com-vitthalmirji/toon4s toon4s: Token-Oriented Object Notation for JVM	42	Emerging	27	Scala
7	mischasigtermans/laravel-toon TOON encoding for Laravel. Encode data for AI/LLMs with ~50% fewer tokens than JSON.	41	Emerging	129	PHP
8	ZON-Format/ZON ZON → 35-70% cheaper LLM prompts than JSON/TOON. Zero overhead.	40	Emerging	66	Python
9	alpkeskin/gotoon Token-Oriented Object Notation for Go – JSON for LLMs at half the token cost	40	Emerging	229	Go
10	HelgeSverre/toon-php Token-Oriented Object Notation - A compact data format for reducing token...	39	Emerging	115	PHP
11	dedsecrattle/toon-rust ֎ Token-Oriented Object Notation (TOON) - Rust implementation	38	Emerging	10	Rust
12	ZON-Format/zon-TS ZON → 35-70% cheaper LLM prompts than JSON/TOON. Zero overhead.	38	Emerging	45	TypeScript
13	thoeltig/file-format-token-accuracy-benchmark Comprehensive benchmark suite measuring token efficiency and accuracy across...	37	Emerging	1	TypeScript
14	dwekat/tooner 🚀 Token-efficient serialization for LLMs - Convert JSON/YAML/TOML to TOON...	36	Emerging	1	TypeScript
15	ason-format/ason ASON (Aliased Serialization Object Notation) is a serialization format...	34	Emerging	10	JavaScript
16	0xCaso/pastoon Auto-convert clipboard JSON to TOON format - 40% fewer LLM tokens. macOS...	32	Emerging	1	TypeScript
17	AndreaIannoli/TOONIFY Universal converter for JSON, YAML, XML, and CSV into the TOON format,...	30	Emerging	16	Rust
18	mamantoha/toon-crystal Crystal implementation of the Token-Oriented Object Notation(TOON)...	28	Experimental	9	Crystal
19	jobmetric/laravel-toon Laravel integration for TOON format: encode/decode JSON data into a...	26	Experimental	26	PHP
20	tapascript/toon-and-json A bunch of source code with Toon and JSON	25	Experimental	6	JavaScript
21	Kelin2025/toon-playground Playground for TOON - JSON for LLMs at half the token cost	24	Experimental	1	TypeScript
22	UsboKirishima/TOONc C library for parsing TOON (Token-Oriented Object Notation), a compact,...	23	Experimental	7	C
23	dagoSte/aton-format-php ATON Format - PHP implementation. Token-efficient data serialization for LLM...	21	Experimental	2	PHP
24	Mctvcell/zon-TS 📦 Convert ZON format to JSON effortlessly with zon-TS, designed for seamless...	21	Experimental	—	TypeScript
25	sstraus/toon_go Token-Oriented Object Notation for Go with encoding / decoding	21	Experimental	—	Go
26	turmex/semtok-format Cut AI costs by 60%. Token-optimized data format that fits 2.5x more data in...	21	Experimental	—	JavaScript
27	nyelzkie/toon-php 🛠️ Implement TOON in PHP for efficient serialization of JSON-like data,...	21	Experimental	—	PHP
28	hwclass/toon-middleware The missing Middleware for reducing LLM API costs through TOON format by...	21	Experimental	2	JavaScript
29	fm4tt0s/gotoon SRE-focused Go proxy for converting JSON to TOON with persistent connection...	21	Experimental	—	Go
30	FutureVision-Labs/toon-parser Token-Oriented Object Notation parser and converter - A more efficient,...	20	Experimental	1	JavaScript
31	ORT-format/ORT Object Record Table - a CSV like structured data format with native object...	18	Experimental	1	Rust
32	dagoSte/aton-format-js ATON Format - TypeScript/JavaScript implementation. Token-efficient data...	17	Experimental	—	TypeScript
33	ZON-Format/.github ZON-Format for LLMs	17	Experimental	—	—
34	martianzhang/json2toon Convert JSON format to TOON	15	Experimental	1	Go
35	RobsonAdvincula/tonn-json-compressor Custom JSON compression algorithm for LLMs — reduce token costs by...	14	Experimental	—	—
36	ason-lab/ason-cpp C++ version for ASON, high performance, replace json, LLM, save tokens	14	Experimental	—	C++
37	ason-lab/ason A schema-driven data format that separates schema from data to reduce...	14	Experimental	—	Shell
38	Sassine/token-optimizer Java library to optimize payload format for minimum token consumption	14	Experimental	3	Java
39	tnfssc/goon Go implementation of the TOON data format.	12	Experimental	1	Go

Comparisons in this category

toon and tonl (67 vs 54) toon and gotoon (67 vs 40) toon and toon-php (67 vs 39) toon and toon4s (67 vs 42) toon and toon-rust (67 vs 38) toon and toon-crystal (67 vs 28) toon and tooner (67 vs 36) laravel-toon and toon-php (41 vs 39) toon-php and laravel-toon (39 vs 26) ZON and zon-TS (40 vs 38)