{
 "metadata": {
  "name": "AI Tokenizer Inflation Ledger 2026: the same text, counted by every model version we can reach",
  "description": "The same fixed corpus (11 text types, 33 items) counted by the token-counting endpoints of 13 Anthropic models, 11 Gemini models and 2 Cohere models, plus offline OpenAI-style counts with tiktoken, with the ratio between successive versions and a bootstrap interval, compared with the providers' own statements. Token counts are not bills.",
  "author": "Vincent Wesley Couey, Nesyona",
  "license": "CC BY 4.0",
  "doi": "10.5281/zenodo.23730116",
  "conceptDoi": "10.5281/zenodo.23730115",
  "doiNote": "doi is version 1 (28 October 2026, Zenodo). conceptDoi covers all versions and always resolves to the latest.",
  "dateModified": "2026-10-28",
  "edition": "2026-10-28",
  "methodSha256": "066cfe21c55a6db0ce68497f7f5a746a05fc6245bf1b1fedd2fe3c56b1a5fffa",
  "corpusManifestSha256": "0bd02f52f2b4e0b0e20992bfadae1592dc24d0cc9876b70ba2275f6b03a9310e",
  "method": "See METHOD.md (committed and hashed before measurement). Same text, count_tokens or countTokens or tokenize, two repeats where stated, overhead-subtracted for Anthropic, ratio per text type, mean over 11 types, percentile bootstrap over types (5,000 resamples, seeded).",
  "limits": [
   "Token counts are not bills. Billing reflects the provider's own accounting; the counts are the providers' estimates and may differ slightly.",
   "Tokenizer behaviour depends on content. A different corpus gives different ratios; we report every text type separately and never only the mean.",
   "The Anthropic count includes a small fixed request overhead that differs by model generation; we subtract a one-character baseline, which understates every count by one token (the baseline character). The effect is at most 1.2 percent on the smallest item and at most 0.16 percent on the longest items we measured, and it moves a ratio between two models by less than that because it affects numerator and denominator alike.",
   "The interval is a bootstrap over 11 text types we chose, not over all possible text; it describes our corpus, not the world.",
   "Gemini model ordering follows the version numbers in the model names because the models list carries no release dates. gemini-2.5-pro was not measured: the provider returned HTTP 404 (\"no longer available to new users\").",
   "Cohere was measured for one pair with one repeat each to respect the trial key limit of 1,000 calls a month.",
   "OpenAI counts are offline tiktoken counts of the text alone. Only models that tiktoken itself maps to an encoding are placed in it; 33 model ids from the models list are unverified and appear in no ratio.",
   "Counting tokens says nothing about quality or about how many tokens a model needs to answer."
  ],
  "files": {
   "data.json": "see the files table",
   "measurements.json": "see the files table",
   "ratios.csv": "see the files table",
   "METHOD.md": "see the files table",
   "METHOD.sha256": "see the files table",
   "README.md": "see the files table",
   "EVIDENCE-MANIFEST.json": "see the files table",
   "corpus/MANIFEST.json": "see the files table"
  }
 },
 "corpus": {
  "items": [
   {
    "id": "prose-en-S",
    "type": "prose-en",
    "length": "S",
    "chars": 356,
    "words": 67,
    "sha256": "cbef4371c962c731ac18d744a564ac0ac36d6adb9900e22189b8241036319e15"
   },
   {
    "id": "prose-en-M",
    "type": "prose-en",
    "length": "M",
    "chars": 1121,
    "words": 208,
    "sha256": "4ca6a37bbd32e0c50f56c7f59c8b6efe09a80f5e83ec809b2f4de80017865c6e"
   },
   {
    "id": "prose-en-L",
    "type": "prose-en",
    "length": "L",
    "chars": 2957,
    "words": 558,
    "sha256": "1c88dd8e5998ede73404f5ce4a4a2721500167399b192535e74b991eee243ede"
   },
   {
    "id": "technical-en-S",
    "type": "technical-en",
    "length": "S",
    "chars": 421,
    "words": 72,
    "sha256": "6c515698c2cfe36b83298d3de98870f47f8052d4c07ead6789886a63ff7d5c94"
   },
   {
    "id": "technical-en-M",
    "type": "technical-en",
    "length": "M",
    "chars": 1206,
    "words": 207,
    "sha256": "626b621feb66961d4f591ce5df3c19bc41598350d14ebd2d73ec2f711f7369d9"
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   {
    "id": "technical-en-L",
    "type": "technical-en",
    "length": "L",
    "chars": 3113,
    "words": 516,
    "sha256": "e2b0c1439691a204972d7fc60d4896896277797684d2491373be6e7526d7fbdf"
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    "id": "code-js-L",
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    "chars": 6938,
    "words": 1032,
    "sha256": "e71e72a7dc8791883d03381752c0095718b8234bfee3a3cdbef2f160ae57c975"
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    "sha256": "a59654eba90d3c69164c1862b0af8788cf0960f89db941c119f54fe476592001"
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   {
    "id": "code-py-M",
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    "id": "code-py-L",
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    "sha256": "4b6c9e72429f3bdad7737742d36c073c90ae3c0b876b0a392794644167e04b17"
   },
   {
    "id": "json-S",
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   {
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    "id": "text-ru-S",
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   {
    "id": "text-ru-M",
    "type": "text-ru",
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    "chars": 1290,
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    "id": "text-ru-L",
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    "chars": 3279,
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    "id": "text-zh-S",
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   {
    "id": "text-zh-M",
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    "type": "text-ar",
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    "sha256": "65c63afe0de5c99223d957ab783cd756270aeb67e0d8c5a4048d4f8cb3dd1d25"
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   {
    "id": "numbers-math-S",
    "type": "numbers-math",
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    "chars": 685,
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    "chars": 2564,
    "words": 468,
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   {
    "id": "numbers-math-L",
    "type": "numbers-math",
    "length": "L",
    "chars": 5909,
    "words": 1040,
    "sha256": "51a0870342953813d1b6e98551d5104404efdd6f6bd592fdfc00589e8bf9b3da"
   },
   {
    "id": "urls-emoji-S",
    "type": "urls-emoji",
    "length": "S",
    "chars": 511,
    "words": 18,
    "sha256": "63afa3d8d7d7404c6d72e142ab815fd13c6b75aedcf62505f6ac4172ebef6f0c"
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   {
    "id": "urls-emoji-M",
    "type": "urls-emoji",
    "length": "M",
    "chars": 1878,
    "words": 66,
    "sha256": "898ff77301421034c01de63475b4dabbbf916a311f687ca107bcff90aab4e24b"
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   {
    "id": "urls-emoji-L",
    "type": "urls-emoji",
    "length": "L",
    "chars": 4274,
    "words": 150,
    "sha256": "4ae624ebee7f8be82e964185ee930fb6111bcf12c7eadbe778ab7b35fc9ebeb2"
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   "prose-en",
   "technical-en",
   "code-js",
   "code-py",
   "json",
   "md-table",
   "text-ru",
   "text-zh",
   "text-ar",
   "numbers-math",
   "urls-emoji"
  ]
 },
 "anthropic": {
  "modelsMeasured": 13,
  "models": [
   {
    "id": "claude-haiku-5-5",
    "display": "Claude Haiku 5.5",
    "created": "2026-10-07",
    "generation": 3,
    "baselineOverheadTokens": 9
   },
   {
    "id": "claude-sonnet-5-5",
    "display": "Claude Sonnet 5.5",
    "created": "2026-09-28",
    "generation": 3,
    "baselineOverheadTokens": 9
   },
   {
    "id": "claude-opus-5-5",
    "display": "Claude Opus 5.5",
    "created": "2026-09-21",
    "generation": 3,
    "baselineOverheadTokens": 9
   },
   {
    "id": "claude-fable-5-1",
    "display": "Claude Fable 5.1",
    "created": "2026-08-28",
    "generation": 3,
    "baselineOverheadTokens": 9
   },
   {
    "id": "claude-opus-5",
    "display": "Claude Opus 5",
    "created": "2026-07-24",
    "generation": 3,
    "baselineOverheadTokens": 7
   },
   {
    "id": "claude-sonnet-5",
    "display": "Claude Sonnet 5",
    "created": "2026-06-29",
    "generation": 3,
    "baselineOverheadTokens": 7
   },
   {
    "id": "claude-fable-5",
    "display": "Claude Fable 5",
    "created": "2026-06-07",
    "generation": 3,
    "baselineOverheadTokens": 7
   },
   {
    "id": "claude-opus-4-8",
    "display": "Claude Opus 4.8",
    "created": "2026-05-28",
    "generation": 3,
    "baselineOverheadTokens": 7
   },
   {
    "id": "claude-opus-4-7",
    "display": "Claude Opus 4.7",
    "created": "2026-04-14",
    "generation": 2,
    "baselineOverheadTokens": 12
   },
   {
    "id": "claude-sonnet-4-6",
    "display": "Claude Sonnet 4.6",
    "created": "2026-02-17",
    "generation": 1,
    "baselineOverheadTokens": 8
   },
   {
    "id": "claude-opus-4-6",
    "display": "Claude Opus 4.6",
    "created": "2026-02-04",
    "generation": 1,
    "baselineOverheadTokens": 8
   },
   {
    "id": "claude-opus-4-5-20251101",
    "display": "Claude Opus 4.5",
    "created": "2025-11-24",
    "generation": 1,
    "baselineOverheadTokens": 8
   },
   {
    "id": "claude-haiku-4-5-20251001",
    "display": "Claude Haiku 4.5",
    "created": "2025-10-15",
    "generation": 1,
    "baselineOverheadTokens": 8
   }
  ],
  "repeatMismatches": [],
  "tokenizerGenerations": [
   {
    "generation": 1,
    "models": [
     "claude-haiku-4-5-20251001",
     "claude-opus-4-5-20251101",
     "claude-opus-4-6",
     "claude-sonnet-4-6"
    ],
    "displayModels": [
     "Claude Haiku 4.5",
     "Claude Opus 4.5",
     "Claude Opus 4.6",
     "Claude Sonnet 4.6"
    ],
    "representative": "claude-haiku-4-5-20251001",
    "baselineOverheadTokens": 8,
    "tokensPerThousandChars": {
     "prose-en": 225.5473,
     "technical-en": 207.4482,
     "code-js": 356.2536,
     "code-py": 321.9331,
     "json": 507.3165,
     "md-table": 466.919,
     "text-ru": 412.303,
     "text-zh": 1187.6326,
     "text-ar": 666.6212,
     "numbers-math": 605.308,
     "urls-emoji": 482.8161
    }
   },
   {
    "generation": 2,
    "models": [
     "claude-opus-4-7"
    ],
    "displayModels": [
     "Claude Opus 4.7"
    ],
    "representative": "claude-opus-4-7",
    "baselineOverheadTokens": 12,
    "tokensPerThousandChars": {
     "prose-en": 301.6954,
     "technical-en": 294.9025,
     "code-js": 439.0523,
     "code-py": 418.6246,
     "json": 557.3889,
     "md-table": 551.5375,
     "text-ru": 412.303,
     "text-zh": 1187.6326,
     "text-ar": 666.6212,
     "numbers-math": 658.7921,
     "urls-emoji": 534.2048
    }
   },
   {
    "generation": 3,
    "models": [
     "claude-opus-4-8",
     "claude-fable-5",
     "claude-sonnet-5",
     "claude-opus-5",
     "claude-fable-5-1",
     "claude-opus-5-5",
     "claude-sonnet-5-5",
     "claude-haiku-5-5"
    ],
    "displayModels": [
     "Claude Opus 4.8",
     "Claude Fable 5",
     "Claude Sonnet 5",
     "Claude Opus 5",
     "Claude Fable 5.1",
     "Claude Opus 5.5",
     "Claude Sonnet 5.5",
     "Claude Haiku 5.5"
    ],
    "representative": "claude-opus-4-8",
    "baselineOverheadTokens": 7,
    "tokensPerThousandChars": {
     "prose-en": 301.6954,
     "technical-en": 294.9025,
     "code-js": 439.0523,
     "code-py": 418.6246,
     "json": 557.3889,
     "md-table": 551.5375,
     "text-ru": 412.303,
     "text-zh": 1187.6326,
     "text-ar": 666.6212,
     "numbers-math": 658.7921,
     "urls-emoji": 534.2048
    }
   }
  ],
  "opus47VersusOpus48": {
   "differingItems": [
    {
     "item": "text-zh-S",
     "opus47": 118,
     "opus48": 117
    },
    {
     "item": "text-zh-M",
     "opus47": 532,
     "opus48": 531
    },
    {
     "item": "text-zh-L",
     "opus47": 1331,
     "opus48": 1330
    },
    {
     "item": "urls-emoji-S",
     "opus47": 268,
     "opus48": 267
    },
    {
     "item": "urls-emoji-M",
     "opus47": 991,
     "opus48": 990
    },
    {
     "item": "urls-emoji-L",
     "opus47": 2277,
     "opus48": 2276
    }
   ],
   "note": "Opus 4.7 and the later models share one tokenizer except on the items listed (if any); the models are grouped as one generation only where every one of the 33 counts is identical."
  },
  "transitions": [
   {
    "label": "Claude Opus 4.5 to Claude Opus 4.6",
    "meanRatio": 1,
    "meanPct": 0,
    "ci95Pct": [
     0,
     0
    ],
    "pooledRatio": 1,
    "minType": {
     "type": "prose-en",
     "ratio": 1,
     "new": 1013,
     "old": 1013
    },
    "maxType": {
     "type": "prose-en",
     "ratio": 1,
     "new": 1013,
     "old": 1013
    },
    "perType": [
     {
      "type": "prose-en",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 1013,
      "tokensOld": 1013
     },
     {
      "type": "technical-en",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 962,
      "tokensOld": 962
     },
     {
      "type": "code-js",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 3704,
      "tokensOld": 3704
     },
     {
      "type": "code-py",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 3185,
      "tokensOld": 3185
     },
     {
      "type": "json",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 3857,
      "tokensOld": 3857
     },
     {
      "type": "md-table",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 2776,
      "tokensOld": 2776
     },
     {
      "type": "text-ru",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 1973,
      "tokensOld": 1973
     },
     {
      "type": "text-zh",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 1981,
      "tokensOld": 1981
     },
     {
      "type": "text-ar",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 2934,
      "tokensOld": 2934
     },
     {
      "type": "numbers-math",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 5649,
      "tokensOld": 5649
     },
     {
      "type": "urls-emoji",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 3200,
      "tokensOld": 3200
     }
    ],
    "family": "opus",
    "from": "claude-opus-4-5-20251101",
    "to": "claude-opus-4-6",
    "fromCreated": "2025-11-24",
    "toCreated": "2026-02-04",
    "sameTokenizerGeneration": true,
    "listPrice": {
     "fromInput": 5,
     "fromOutput": 25,
     "toInput": 5,
     "toOutput": 25,
     "inputChangePct": 0,
     "outputChangePct": 0,
     "effectiveInputCostChangePct": 0,
     "effectiveProseInputCostChangePct": 0
    }
   },
   {
    "label": "Claude Opus 4.6 to Claude Opus 4.7",
    "meanRatio": 1.1601,
    "meanPct": 16.0066,
    "ci95Pct": [
     8.2089,
     24.5549
    ],
    "pooledRatio": 1.138,
    "minType": {
     "type": "text-ru",
     "ratio": 1,
     "new": 1973,
     "old": 1973
    },
    "maxType": {
     "type": "technical-en",
     "ratio": 1.4095634095634095,
     "new": 1356,
     "old": 962
    },
    "perType": [
     {
      "type": "prose-en",
      "ratio": 1.3327,
      "pct": 33.2675,
      "tokensNew": 1350,
      "tokensOld": 1013
     },
     {
      "type": "technical-en",
      "ratio": 1.4096,
      "pct": 40.9563,
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   "docsReadUtc": "2026-10-28",
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 },
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      "tokensNew": 3099,
      "tokensOld": 3108
     },
     {
      "type": "code-py",
      "ratio": 1.0066,
      "pct": 0.6606,
      "tokensNew": 2743,
      "tokensOld": 2725
     },
     {
      "type": "json",
      "ratio": 1.0105,
      "pct": 1.0494,
      "tokensNew": 3274,
      "tokensOld": 3240
     },
     {
      "type": "md-table",
      "ratio": 0.9907,
      "pct": -0.9294,
      "tokensNew": 2345,
      "tokensOld": 2367
     },
     {
      "type": "text-ru",
      "ratio": 0.6065,
      "pct": -39.35,
      "tokensNew": 1381,
      "tokensOld": 2277
     },
     {
      "type": "text-zh",
      "ratio": 0.6855,
      "pct": -31.4501,
      "tokensNew": 1456,
      "tokensOld": 2124
     },
     {
      "type": "text-ar",
      "ratio": 0.4563,
      "pct": -54.3729,
      "tokensNew": 1466,
      "tokensOld": 3213
     },
     {
      "type": "numbers-math",
      "ratio": 1,
      "pct": 0,
      "tokensNew": 5088,
      "tokensOld": 5088
     },
     {
      "type": "urls-emoji",
      "ratio": 0.9489,
      "pct": -5.1136,
      "tokensNew": 2338,
      "tokensOld": 2464
     }
    ],
    "from": "cl100k_base",
    "to": "o200k_base"
   }
  ],
  "tokensPerThousandChars": {
   "cl100k_base": {
    "prose-en": 217.6556,
    "technical-en": 190.9249,
    "code-js": 298.5152,
    "code-py": 274.9186,
    "json": 425.0058,
    "md-table": 395.9109,
    "text-ru": 474.252,
    "text-zh": 1268.6312,
    "text-ar": 726.127,
    "numbers-math": 545.1385,
    "urls-emoji": 374.1934
   },
   "o200k_base": {
    "prose-en": 216.728,
    "technical-en": 189.8227,
    "code-js": 297.5943,
    "code-py": 276.7324,
    "json": 429.5404,
    "md-table": 392.6604,
    "text-ru": 289.5334,
    "text-zh": 868.068,
    "text-ar": 327.8019,
    "numbers-math": 545.1385,
    "urls-emoji": 354.0625
   }
  },
  "note": "offline text-only counts; no message framing. A model is placed in an encoding only where tiktoken encoding_for_model returned it; the models tiktoken does not know are listed as unverified and are in no ratio."
 },
 "crossVendorProse": {
  "item": "prose-en-L",
  "words": 558,
  "chars": 2957,
  "rows": [
   {
    "vendor": "Cohere",
    "tokenizer": "command-a-plus-05-2026",
    "models": [
     "command-a-plus-05-2026"
    ],
    "tokens": 627
   },
   {
    "vendor": "Google",
    "tokenizer": "gemini-2.5-flash-lite and 9 other Gemini models with identical counts",
    "models": [
     "gemini-2.5-flash-lite",
     "gemini-2.5-flash",
     "gemini-3-flash-preview",
     "gemini-3.1-pro-preview",
     "gemini-3.1-flash-lite",
     "gemini-3.5-flash",
     "gemini-3.5-flash-lite",
     "gemini-3.6-flash",
     "gemini-3.7-flash",
     "gemini-3.8-flash"
    ],
    "tokens": 637
   },
   {
    "vendor": "OpenAI (offline tiktoken)",
    "tokenizer": "o200k_base",
    "models": [
     "see modelsMappedByTiktoken"
    ],
    "tokens": 639
   },
   {
    "vendor": "OpenAI (offline tiktoken)",
    "tokenizer": "cl100k_base",
    "models": [
     "see modelsMappedByTiktoken"
    ],
    "tokens": 644
   },
   {
    "vendor": "Cohere",
    "tokenizer": "command-a-03-2025",
    "models": [
     "command-a-03-2025"
    ],
    "tokens": 649
   },
   {
    "vendor": "Google",
    "tokenizer": "gemini-4-argon",
    "models": [
     "gemini-4-argon"
    ],
    "tokens": 664
   },
   {
    "vendor": "Anthropic",
    "tokenizer": "Claude tokenizer generation 1",
    "models": [
     "Claude Haiku 4.5",
     "Claude Opus 4.5",
     "Claude Opus 4.6",
     "Claude Sonnet 4.6"
    ],
    "tokens": 671
   },
   {
    "vendor": "Anthropic",
    "tokenizer": "Claude tokenizer generation 2",
    "models": [
     "Claude Opus 4.7"
    ],
    "tokens": 896
   },
   {
    "vendor": "Anthropic",
    "tokenizer": "Claude tokenizer generation 3",
    "models": [
     "Claude Opus 4.8",
     "Claude Fable 5",
     "Claude Sonnet 5",
     "Claude Opus 5",
     "Claude Fable 5.1",
     "Claude Opus 5.5",
     "Claude Sonnet 5.5",
     "Claude Haiku 5.5"
    ],
    "tokens": 896
   }
  ]
 }
}