Parsing gigabytes of JSON per second : used by Facebook/Meta Velox, the Node.js runtime, ClickHouse, WatermelonDB, Apache Doris, Milvus, StarRocks
This report presents the forensic synthetic code analysis of simdjson/simdjson, a C++ project with 23,952 GitHub stars. SynthScan v2.0 examined 145,087 lines of code across 701 source files, recording 526 pattern matches distributed across 12 syntactic categories. The overall adjusted score of 3.7 places this repository in the Likely human-written band.
The scanner applied 160+ deterministic lexical heuristics, multi-line block detectors, abstract syntax tree depth profilers, and a cross-file Jaccard similarity matrix to construct a statistically normalised synthetic code estimate. All matches are individually weighted by severity coefficient and contextual multiplier before summation, and the resulting headline score is temporally discounted to account for the repository's development history relative to the commercial emergence of large language model coding tooling (November 2022 onward).
This chart maps the temporal evolution of the adjusted synthetic code score across successive scan runs. An upward trajectory indicates ongoing incorporation of AI-generated code or expanding LLM-assisted scaffolding; a stable or declining trajectory may reflect active human refactoring, code removal, or the adoption of stricter authorship policies. The dashed secondary line (right axis) independently tracks total raw pattern hit count, which can diverge from the normalised score when codebase size changes significantly between scans.
Classifies detected patterns by their diagnostic confidence and structural impact. CRITICAL patterns (coefficient 10) represent definitive synthetic signatures — hallucinated imports, explicit LLM attribution metadata — virtually never produced by human authors. HIGH (5) indicates strong structural tells such as cross-file repetition or cross-linguistic idioms. MEDIUM (2) covers recognisable conversational padding and AI-specific vocabulary. LOW (1) captures subtle indicators like tautological comments and generic boilerplate that require density to carry independent signal.
This horizontal bar chart decomposes the repository's raw synthetic code score by top-level directory, allowing you to pinpoint precisely which modules or components carry the highest AI authorship density. Directories with disproportionately high scores relative to their size warrant targeted manual review: concentrated AI signatures often trace back to mass-generated configuration layers, auto-ported test suites, LLM-scaffolded boilerplate classes, or entire subsystems authored under heavy copilot assistance. Use this view to prioritise your human code-review effort.
The scanner identified 526 distinct pattern matches across 12 syntactic categories. Each entry below represents a discrete location in the source code where the engine recorded a statistically significant AI authorship indicator. Expand any category row to inspect the individual file paths, line numbers, code snippets, and the lexical context (CODE, COMMENT, or STRING) in which each match was detected.
Reading the findings table: The Severity column indicates the diagnostic confidence level (CRITICAL / HIGH / MEDIUM / LOW). The Context column identifies whether the match occurred inside executable code, an inline comment, or a string literal — comment-context matches receive a ×1.5 weight because LLMs systematically over-annotate. The ⚡ bolt icon marks clustered matches: three or more patterns within a 10-line window, each receiving an additional ×1.5 density multiplier as dense clusters constitute far stronger evidence of synthetic authorship than isolated hits.
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | .travis.yml | 141 | key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key' | COMMENT |
| LOW | benchmark/benchmarker.h | 1 | #ifndef __BENCHMARKER_H | COMMENT |
| LOW | benchmark/benchmarker.h | 21 | #include <chrono> | COMMENT |
| LOW | benchmark/benchmarker.h | 261 | event_collector& collector; | COMMENT |
| LOW | benchmark/benchfeatures.cpp | 1 | #include <counters/event_counter.h> | COMMENT |
| LOW | benchmark/benchfeatures.cpp | 21 | #include <iomanip> | COMMENT |
| LOW | benchmark/bench_ondemand.cpp | 1 | #include "simdjson.h" | COMMENT |
| LOW | benchmark/bench_ondemand.cpp | 21 | #include <nlohmann/json.hpp> | COMMENT |
| LOW | benchmark/bench_ondemand.cpp | 41 | COMMENT | |
| LOW | benchmark/bench_ondemand.cpp | 61 | #include "distinct_user_id/simdjson_ondemand_json_pointer.h" | COMMENT |
| LOW | benchmark/bench_ondemand.cpp | 81 | #if SIMDJSON_COMPETITION_ONDEMAND_SAJSON | COMMENT |
| LOW | benchmark/bench_ondemand.cpp | 101 | #if SIMDJSON_COMPETITION_SAX | COMMENT |
| LOW | benchmark/bench_ondemand.cpp | 121 | #include "kostya/nlohmann_json.h" | COMMENT |
| LOW | benchmark/bench_ondemand.cpp | 141 | #include "large_random/nlohmann_json.h" | COMMENT |
| LOW | benchmark/distinct_user_id/rapidjson_sax.h | 61 | #endif // SIMDJSON_COMPETITION_RAPIDJSON | COMMENT |
| LOW | …eflect/twitter_benchmark/benchmark_parsing_twitter.cpp | 1 | #include <cassert> | COMMENT |
| LOW | …/twitter_benchmark/benchmark_serialization_twitter.cpp | 1 | #include <cassert> | COMMENT |
| LOW | benchmark/static_reflect/serde-benchmark/lib.rs | 241 | // FFI Overhead Measurement Functions | COMMENT |
| LOW | …log_benchmark/benchmark_serialization_citm_catalog.cpp | 1 | #include <cassert> | COMMENT |
| LOW | …lect/citm_catalog_benchmark/benchmark_parsing_citm.cpp | 1 | #include <cassert> | COMMENT |
| LOW | benchmark/partial_tweets/tweet.h | 1 | #pragma once | COMMENT |
| LOW | benchmark/dom/perfdiff.cpp | 1 | #include <cstdio> | COMMENT |
| LOW | benchmark/dom/parse.cpp | 1 | #include <counters/event_counter.h> | COMMENT |
| LOW | benchmark/dom/parse.cpp | 21 | #include <iostream> | COMMENT |
| LOW | tools/minify.cpp | 1 | #include <chrono> | COMMENT |
| LOW | tools/json2json.cpp | 1 | #include <iostream> | COMMENT |
| LOW | include/simdjson.h | 41 | #include "simdjson/simdjson_version.h" | COMMENT |
| LOW | include/simdjson.h | 61 | #include "simdjson/compile_time_json.h" | COMMENT |
| LOW | include/simdjson/builtin.h | 1 | #ifndef SIMDJSON_BUILTIN_H | COMMENT |
| LOW | include/simdjson/builtin.h | 21 | #elif SIMDJSON_BUILTIN_IMPLEMENTATION_IS(westmere) | COMMENT |
| LOW | include/simdjson/fallback.h | 1 | #ifndef SIMDJSON_FALLBACK_H | COMMENT |
| LOW | include/simdjson/dom.h | 1 | #ifndef SIMDJSON_DOM_H | COMMENT |
| LOW | include/simdjson/dom.h | 21 | #include "simdjson/internal/tape_ref-inl.h" | COMMENT |
| LOW | include/simdjson/ppc64.h | 1 | #ifndef SIMDJSON_PPC64_H | COMMENT |
| LOW | include/simdjson/rvv-vls.h | 1 | #ifndef SIMDJSON_RVV_VLS_H | COMMENT |
| LOW | include/simdjson/haswell.h | 1 | #ifndef SIMDJSON_HASWELL_H | COMMENT |
| LOW | include/simdjson/convert-inl.h | 121 | #endif // SIMDJSON_SUPPORTS_CONCEPTS | COMMENT |
| LOW | include/simdjson/icelake.h | 1 | #ifndef SIMDJSON_ICELAKE_H | COMMENT |
| LOW | include/simdjson/portability.h | 1 | #ifndef SIMDJSON_PORTABILITY_H | COMMENT |
| LOW | include/simdjson/portability.h | 41 | COMMENT | |
| LOW | include/simdjson/portability.h | 61 | COMMENT | |
| LOW | include/simdjson/portability.h | 81 | // We are not using GCC, so we assume that we can support runtime dispatch for LASX. | COMMENT |
| LOW | include/simdjson/portability.h | 101 | #elif defined(__PPC__) || defined(_M_PPC) | COMMENT |
| LOW | include/simdjson/portability.h | 121 | #define SIMDJSON_STRINGIFY(a,...) SIMDJSON_CAT_IMPLEMENTATION_(a, __VA_ARGS__) | COMMENT |
| LOW | include/simdjson/portability.h | 141 | // | COMMENT |
| LOW | include/simdjson/portability.h | 161 | #endif // defined(SIMDJSON_IS_X86_64) || defined(SIMDJSON_IS_LSX) | COMMENT |
| LOW | include/simdjson/portability.h | 181 | // Lack of compiler optimization may generate high stack usage. | COMMENT |
| LOW | include/simdjson/portability.h | 201 | #define simdjson_pure | COMMENT |
| LOW | include/simdjson/portability.h | 221 | #define simdjson_strncasecmp _strnicmp | COMMENT |
| LOW | include/simdjson/portability.h | 241 | #endif | COMMENT |
| LOW | include/simdjson/portability.h | 261 | #elif defined(__MVS__) | COMMENT |
| LOW | include/simdjson/portability.h | 281 | #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ | COMMENT |
| LOW | include/simdjson/portability.h | 301 | // On Windows the class is disabled by default and must be explicitly | COMMENT |
| LOW | include/simdjson/portability.h | 321 | // simply does not exist — any attempt to use it fails at compile time | COMMENT |
| LOW | include/simdjson/common_defs.h | 21 | double from_chars(const char *first) noexcept; | COMMENT |
| LOW | include/simdjson/common_defs.h | 41 | #define SIMDJSON_BEGIN_DEBUG_BLOCK(name) __asm volatile("# LLVM-MCA-BEGIN " #name); | COMMENT |
| LOW | include/simdjson/common_defs.h | 61 | #define simdjson_unused | COMMENT |
| LOW | include/simdjson/common_defs.h | 81 | #endif | COMMENT |
| LOW | include/simdjson/common_defs.h | 101 | COMMENT | |
| LOW | include/simdjson/common_defs.h | 141 | SIMDJSON_DISABLE_GCC_WARNING(-Wunused-variable) \ | COMMENT |
| 415 more matches not shown… | ||||
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | benchmark/benchmark_reflection_usage_compilation.sh | 322 | "name": "John Doe", | CODE |
| LOW | benchmark/benchmark_reflection_usage_compilation.sh | 327 | "street": "123 Main St", | CODE |
| LOW | benchmark/benchmark_reflection_usage_compilation.sh | 393 | "name": "John Doe", | CODE |
| LOW | benchmark/benchmark_reflection_usage_compilation.sh | 398 | "street": "123 Main St", | CODE |
| LOW | benchmark/accessor_performance/accessor_benchmark.h | 16 | "street": "123 Main St", | CODE |
| LOW | tests/ondemand/compile_time_json_path_tests.cpp | 47 | "name": "John Doe", | CODE |
| LOW | tests/ondemand/compile_time_json_path_tests.cpp | 58 | "street": "123 Main St", | CODE |
| LOW | tests/ondemand/compile_time_json_path_tests.cpp | 133 | ASSERT_EQUAL(name, "John Doe"); | CODE |
| LOW | tests/ondemand/compile_time_json_path_tests.cpp | 178 | ASSERT_EQUAL(street, "123 Main St"); | CODE |
| LOW | tests/ondemand/compile_time_json_pointer_tests.cpp | 47 | "name": "John Doe", | CODE |
| LOW | tests/ondemand/compile_time_json_pointer_tests.cpp | 96 | "street": "123 Main St", | CODE |
| LOW | tests/ondemand/compile_time_json_pointer_tests.cpp | 120 | ASSERT_EQUAL(name, "John Doe"); | CODE |
| LOW | tests/ondemand/compile_time_json_pointer_tests.cpp | 432 | ASSERT_EQUAL(street, "123 Main St"); | CODE |
| LOW | tests/ondemand/compile_time_json_pointer_tests.cpp | 527 | ASSERT_EQUAL(name, "John Doe"); | CODE |
| LOW | tests/builder/static_reflection_comprehensive_tests.cpp | 577 | Person person{"John Doe", 30, "john@example.com", std::nullopt}; | CODE |
| LOW | tests/builder/static_reflection_comprehensive_tests.cpp | 592 | ASSERT_EQUAL(name, "John Doe"); | CODE |
| LOW | tests/builder/static_reflection_comprehensive_tests.cpp | 598 | Person person{"Jane Smith", 25, "jane@example.com", "555-1234"}; | CODE |
| LOW | tests/builder/static_reflection_comprehensive_tests.cpp | 617 | ASSERT_EQUAL(phone, "555-1234"); | CODE |
| LOW | tests/builder/static_reflection_comprehensive_tests.cpp | 672 | Company company{"TechCorp", {"123 Main St", "San Francisco", "94105"}, 500}; | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 42 | // Step 1: Serialize to minified JSON | COMMENT |
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 49 | // Step 2: Reformat with FracturedJson | COMMENT |
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 73 | // Step 1: Extract fields to minified JSON | COMMENT |
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 80 | // Step 2: Reformat with FracturedJson | COMMENT |
| LOW⚡ | src/to_chars.cpp | 919 | // Step 1: Schubfach multiplier calculation. | COMMENT |
| LOW⚡ | src/to_chars.cpp | 928 | // Step 2: Try larger divisor; remove trailing zeros if necessary. | COMMENT |
| LOW | src/to_chars.cpp | 958 | // Step 3: Find the significand with the smaller divisor. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 42 | // Step 1: Serialize to minified JSON | COMMENT |
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 49 | // Step 2: Reformat with FracturedJson | COMMENT |
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 73 | // Step 1: Extract fields to minified JSON | COMMENT |
| LOW⚡ | …lude/simdjson/generic/builder/fractured_json_builder.h | 80 | // Step 2: Reformat with FracturedJson | COMMENT |
| LOW⚡ | src/to_chars.cpp | 919 | // Step 1: Schubfach multiplier calculation. | COMMENT |
| LOW⚡ | src/to_chars.cpp | 928 | // Step 2: Try larger divisor; remove trailing zeros if necessary. | COMMENT |
| LOW | src/to_chars.cpp | 958 | // Step 3: Find the significand with the smaller divisor. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | style/run-clang-format.py | 36 | CODE | |
| LOW | style/run-clang-format.py | 163 | CODE | |
| LOW | scripts/detect_nonascii_sourcefiles.py | 5 | CODE | |
| LOW | singleheader/amalgamate.py | 717 | CODE | |
| LOW | singleheader/amalgamate.py | 375 | CODE | |
| LOW | singleheader/amalgamate.py | 540 | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| HIGH | tools/release.py | 188 | print("to issue release, enter \n git commit -a && git push && git tag -a v"+toversionstring(*newversion)+" -m \"versi | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | benchmark/benchmark_reflection_usage_compilation.sh | 57 | # ───────────────────────────── BOX-PRINT HELPER ──────────────────────────── | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | tools/release.py | 8 | CODE | |
| LOW | style/run-clang-format.py | 11 | CODE | |
| LOW | style/run-clang-format.py | 11 | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | style/run-clang-format.py | 97 | except Exception as e: | CODE |
| MEDIUM | style/run-clang-format.py | 91 | def run_clang_format_diff_wrapper(args, file): | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | style/run-clang-format.py | 91 | def run_clang_format_diff_wrapper(args, file): | CODE |
| LOW | singleheader/amalgamate.py | 375 | def validate_free_dependency_file(self): | STRING |
| LOW | singleheader/amalgamate.py | 423 | def validate_free_dependency_files(self): | STRING |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | benchmark/benchmark_reflection_usage_compilation.sh | 167 | # Check if we found a working compiler | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | fuzz/ossfuzz.sh | 9 | # make sure to exit on problems | COMMENT |