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 45 llm serialization formats tools tracked. 1 score above 70 (verified tier). The highest-rated is toon-format/toon at 84/100 with 23,207 stars and 1,595,658 monthly downloads. 2 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,...	84	Verified	23,207	TypeScript
2	tonl-dev/tonl TONL (Token-Optimized Notation Language)	64	Established	826	TypeScript
3	dweve-ai/hedl Token-efficient data serialization for LLM/AI. 50% fewer tokens than JSON,...	51	Established	65	Rust
4	toon-format/toon-java ☕ Community-driven Java implementation of TOON	48	Emerging	140	Java
5	ISON-format/ison 🔥 🔥 Alternative to JSON 🔥 🔥	39	Emerging	126	Python
6	com-vitthalmirji/toon4s toon4s: Token-Oriented Object Notation for JVM	38	Emerging	27	Scala
7	0xCaso/pastoon Auto-convert clipboard JSON to TOON format - 40% fewer LLM tokens. macOS...	37	Emerging	1	TypeScript
8	dwekat/tooner 🚀 Token-efficient serialization for LLMs - Convert JSON/YAML/TOML to TOON...	37	Emerging	1	TypeScript
9	mischasigtermans/laravel-toon TOON encoding for Laravel. Encode data for AI/LLMs with ~50% fewer tokens than JSON.	37	Emerging	129	PHP
10	alpkeskin/gotoon Token-Oriented Object Notation for Go – JSON for LLMs at half the token cost	36	Emerging	229	Go
11	ZON-Format/ZON ZON → 35-70% cheaper LLM prompts than JSON/TOON. Zero overhead.	36	Emerging	66	Python
12	thoeltig/file-format-token-accuracy-benchmark Comprehensive benchmark suite measuring token efficiency and accuracy across...	35	Emerging	1	TypeScript
13	HelgeSverre/toon-php Token-Oriented Object Notation - A compact data format for reducing token...	35	Emerging	115	PHP
14	ZON-Format/zon-TS ZON → 35-70% cheaper LLM prompts than JSON/TOON. Zero overhead.	34	Emerging	45	TypeScript
15	dedsecrattle/toon-rust ֎ Token-Oriented Object Notation (TOON) - Rust implementation	34	Emerging	10	Rust
16	jimmystridh/toon-rs 🎨 Rust implementation of TOON (Token-Oriented Object Notation) - A...	34	Emerging	5	Rust
17	ason-format/ason ASON (Aliased Serialization Object Notation) is a serialization format...	30	Emerging	10	JavaScript
18	dagoSte/aton-format ATON Format - Python implementation. Token-efficient data serialization for...	28	Experimental	1	Python
19	mamantoha/toon-crystal Crystal implementation of the Token-Oriented Object Notation(TOON)...	27	Experimental	9	Crystal
20	AndreaIannoli/TOONIFY Universal converter for JSON, YAML, XML, and CSV into the TOON format,...	26	Experimental	16	Rust
21	waynerchen223/json-toon-converter-compact 🔄 Convert JSON to TOON format effortlessly with this TypeScript library,...	22	Experimental	—	TypeScript
22	Oluwaferanmi3/tooner 🔄 Convert JSON, YAML, and TOML to TOON format for token-efficient...	22	Experimental	—	TypeScript
23	jobmetric/laravel-toon Laravel integration for TOON format: encode/decode JSON data into a...	22	Experimental	26	PHP
24	nyelzkie/toon-php 🛠️ Implement TOON in PHP for efficient serialization of JSON-like data,...	22	Experimental	—	PHP
25	fbosch/opencode-toon-plugin 🎒 Compact large JSON tool output in OpenCode with TOON.	22	Experimental	—	TypeScript
26	Mctvcell/zon-TS 📦 Convert ZON format to JSON effortlessly with zon-TS, designed for seamless...	22	Experimental	—	TypeScript
27	tapascript/toon-and-json A bunch of source code with Toon and JSON	21	Experimental	6	JavaScript
28	Kelin2025/toon-playground Playground for TOON - JSON for LLMs at half the token cost	20	Experimental	1	TypeScript
29	sstraus/toon_go Token-Oriented Object Notation for Go with encoding / decoding	19	Experimental	—	Go
30	UsboKirishima/TOONc C library for parsing TOON (Token-Oriented Object Notation), a compact,...	19	Experimental	7	C
31	turmex/semtok-format Cut AI costs by 60%. Token-optimized data format that fits 2.5x more data in...	19	Experimental	—	JavaScript
32	fm4tt0s/gotoon SRE-focused Go proxy for converting JSON to TOON with persistent connection...	19	Experimental	—	Go
33	dagoSte/aton-format-php ATON Format - PHP implementation. Token-efficient data serialization for LLM...	17	Experimental	2	PHP
34	hwclass/toon-middleware The missing Middleware for reducing LLM API costs through TOON format by...	17	Experimental	2	JavaScript
35	ason-format/zed-extension Compress and decompress JSON using the ASON format directly in Zed IDE....	16	Experimental	1	Rust
36	ORT-format/ORT Object Record Table - a CSV like structured data format with native object...	16	Experimental	1	Rust
37	FutureVision-Labs/toon-parser Token-Oriented Object Notation parser and converter - A more efficient,...	16	Experimental	1	JavaScript
38	dagoSte/aton-format-js ATON Format - TypeScript/JavaScript implementation. Token-efficient data...	15	Experimental	—	TypeScript
39	ZON-Format/.github ZON-Format for LLMs	15	Experimental	—	—
40	martianzhang/json2toon Convert JSON format to TOON	15	Experimental	1	Go
41	ason-lab/ason A schema-driven data format that separates schema from data to reduce...	14	Experimental	—	Shell
42	RobsonAdvincula/tonn-json-compressor Custom JSON compression algorithm for LLMs — reduce token costs by...	14	Experimental	—	—
43	ason-lab/ason-cpp C++ version for ASON, high performance, replace json, LLM, save tokens	14	Experimental	—	C++
44	Sassine/token-optimizer Java library to optimize payload format for minimum token consumption	10	Experimental	3	Java
45	tnfssc/goon Go implementation of the TOON data format.	10	Experimental	1	Go

Comparisons in this category

toon and tonl (84 vs 64) toon and gotoon (84 vs 36) toon and toon-php (84 vs 35) toon and ZON (84 vs 36) toon and zon-TS (84 vs 34) toon and toon4s (84 vs 38) toon and TOONIFY (84 vs 26) toon and toon-rust (84 vs 34) toon and toon-crystal (84 vs 27) toon and toon-rs (84 vs 34)