A plain-language walkthrough of every tool in the Derby Owners Club Tools Suite: what it is, why it helps, and exactly how to use it. If a tool ever feels confusing, find its section below and follow the steps.
The Suite lives at doc.johnreevesiii.com/tools (also tools.johnreevesiii.com). Everything runs in your web browser. There is nothing to install, no account, and once a page has loaded it works offline. Nothing you load is ever uploaded.
Opening a tool. Go to the Suite address above. You will see a landing page with four tabs across the top. Click a tab to see the tools in that group, then click a tool's card to open it. Each tool is its own page; use your browser's Back button to return to the landing page.
The four tabs (pick by what you want to do):
The colored tags on each tool tell you the risk:
A note on game versions. DOC exists in four builds: Rev C (World Edition), Rev D (World Edition EX), DOC 2000 (Japanese), and DOC '99 (Japanese, the original). They are different games with different horses, tracks, and food. Most tools let you pick the version; always set it to the one you actually play, because data does not carry across versions.
Several tools can load one of your horses. A horse lives in a small file, and there are two kinds:
.card is the newer format used by the home setup (a 207-byte file)..raw is the older format from the physical card reader.You do not need to know which you have. Every tool that loads a horse now accepts both, and reads exactly the same horse from either. Where do these files come from? The Stable Management System (in Mod & Inspect) creates and saves them, and the home game saves your horses as cards. If you only play and have never exported a horse, that is fine: every Play & Plan tool also works with no file, by typing your horse's numbers in yourself.
Japanese cards carry the horse's name and pedigree but not its stats (those live in the cabinet). Tools will tell you this plainly rather than failing.
These answer everyday questions. None of them require a file.
What it is: a plain-language page of the mechanics the game never shows you, decoded from the ROM. Breeding's favorable pairs, why externals matter, the post-race bond multipliers, condition breakpoints.
Why it helps: these are the things experienced players guessed at for years. Knowing them changes how you breed, feed, and race.
How to use it:
What it is: tells you which foods raise the stat you care about, and totals up a feeding plan.
Why it helps: instead of guessing what to feed, you see the exact ranked gains and can plan a session.
How to use it:
Tips: the three main stats are confirmed from the ROM; a few extra columns are unconfirmed hidden effects and are shown faintly. Japanese cards have no stats to project, so the tool will say so.
What it is: enter (or load) your horse and see how it would do: its best distance, how it places against a real field, and its win odds.
Why it helps: test a horse and a trip before you commit a real race to it.
How to use it:
Tips: the boxes accept two- and three-digit values. The big table below is the full CPU roster; click a column header to sort it, and use the search box to find a horse.
What it is: the player-friendly face of breeding. Pick two parents and see the foal you will likely get.
Why it helps: plan a pairing before you spend the in-game breeding on it.
How to use it:
Tips: because breeding has a built-in random wobble, the tool shows a range (low to high), not one fixed number. The deeper version with the best-mate finder is the Breeding Lab in Theorycraft.
What it is: a browser of every CPU horse you might race against, with a power ranking.
Why it helps: spot a soft field, or learn the field before a key race.
How to use it:
The full-depth versions of the planning tools.
What it is: the complete breeding tool. The byte-exact foal formula, a Monte-Carlo run over thousands of foals, a best-mate finder, and the inherited aptitude/style detail.
Why it helps: this is where you optimize a line, not just check one pairing.
How to use it:
Tips: the best-mate finder only suggests mates from the selected version, because each version is a separate game; the header says which version it is searching. The "Nerd details" toggle (bottom right) reveals the inherited aptitude/style masks and the model's provenance.
What it is: the deeper race tool: a tick-by-tick simulation calibrated against live game telemetry, plus the strength and best-trip estimators.
How to use it: same as the Race Simulator (it is the same page with the full detail shown). Use the Your-horse row or load a card, set the trip, and run.
What it is: all 244 CPU horses across all four versions, every field, with a power column and CSV/JSON export.
How to use it: set the version, sort and filter, and use the export buttons if you want the data in a spreadsheet.
What it is: every course, its distance and surface, and the G1 race schedule per version, with the English and Japanese venue names mapped.
How to use it: pick a version and browse. Use it to plan which races to target and when.
What it is: shows exactly what changed between the four builds: per-horse stat changes, renames, and roster differences.
Why it helps: answers "which version is the best meta" with evidence.
How to use it: open it and read the comparison; pick the two versions you are weighing.
What it is: one horse across all four versions, English to katakana and romaji, lined up by id, with Rev D renames flagged.
How to use it: search a name to see its equivalents in the other versions.
These edit your own files. The ROM editors write real bytes, so keep a backup first.
What it is: the full card studio. Create, edit, and organize your horse cards, and manage your stable. This is the tool that produces the .card files the Play & Plan tools load.
Why it helps: it is the home base for your horses outside the game.
How to use it:
.card or .raw, or New to start a horse from scratch.Tips: personality is preserved exactly when you save (an older version could change it by accident; that is fixed). For the meaning of any single byte, see the Card Byte Map.
What it is: a reference page showing what every byte on a player card does, including where the old community maps were wrong.
How to use it: read it before editing a card by hand. It is a reference, not an editor.
What it is: an editor for the game's own data inside your ROM: the 244-horse table (every stat, name, grade, style) and an Enable-Beer patch. Exports a patched .ic22 ROM.
How to use it:
.ic22. The tool auto-detects the version.Tips: it uses per-version profiles, so it will not blindly cross-patch the versions that genuinely differ.
What it is: edits the feed table values and offers a one-click "Enable Beer," exporting a byte-exact patched ROM.
How to use it: back up, load the ROM, change values or click Enable Beer, export.
What it is: pulls every in-game text string so you can edit it, with a byte-budget meter, and exports a patched ROM. Round-trips through CSV/JSON.
How to use it: back up, load the ROM, edit strings (watch the byte budget), export.
What it is: drop two cards and get a byte-exact decode, a field-by-field diff, and each horse's pedigree against the breeding pool.
Why it helps: compare two horses, or check a card you were given.
How to use it: drag or click to load Card A and (optionally) Card B. Accepts .card and .raw, US and Japanese.
What it is: edit a Japanese card's kana name, sire, and dam, and cross-reference it to its English twin.
How to use it: load a Japanese card, edit the kana fields with the built-in keyboard, and save.
What it is: drop a .ic22 and it identifies the exact version, then proves it by decoding horse #1.
How to use it: load any DOC ROM dump to confirm what it is before you work on it.
What it is: the open-source card codec (a Python library), for developers who want to read or write cards in their own scripts.
How to use it: it is code, not a web page. Get it from the GitHub link in the Suite footer.
For real or emulated cabinets.
What it is: a live community leaderboard at doc.johnreevesiii.com that collects the best course times saved on players' machines and ranks every course by the fastest record, per ROM version. The in-package Record Uploader finds your cabinet save and submits it — you just add your stable and owner name.
Why a board time can differ from the time you saw in the game. When you finish a race, the RESULT screen shows your exact finishing time to a hundredth of a second — for example 1.23.62. But the original 2001 arcade game only permanently saves a track record rounded to the nearest 1/20 of a second (0.05 s). The value it writes into the cabinet's memory for that record is 1.23.65, not 1.23.62 — the precise hundredths you saw are never stored. We confirmed this against the raw save file: the exact time appears nowhere in it. The game keeps only the rounded record.
The online leaderboard reads that saved record, so:
This is the game's behavior, not the leaderboard's. The board faithfully shows the exact record the cabinet permanently kept. And because every player's time is rounded the same way, by the same game, the rankings are fair: everyone is measured identically, so the saved record is the consistent, comparable number for the board. One side effect of the rounding is that two runs within 0.05 s of each other can tie on the board, where the live screen would have split them.
What it is: drop a cabinet save (.sram / .eeprom) and read its money leaderboards, track records, and bookkeeping. Read-only.
How to use it: load the save file; browse the leaderboards and records.
What it is: edits the resume-counter in both save regions and recomputes the checksum when it can.
How to use it: back up the save, load it, adjust the counter, export.
These also appear here for preservation work: identify a dump, document what changed between builds, and search the full in-game text catalog by version, block, and offset.
Do I need the game to use these? No. The planning tools work on their own. The editors need your own ROM, card, or save files.
Is anything uploaded? No. Everything runs in your browser. You can disconnect from the internet after a page loads and it will still work.
A tool said my card is Japanese and has no stats. That is correct: Japanese cards store identity and pedigree only; the stats live in the cabinet. Use the name and pedigree, or load a World Edition card for the stat tools.
I loaded a horse and a stat looks capped. Bred internal stats cap at 45, and several tools show that cap. The higher numbers you see during a horse's life are its racing stats, which training and food pump up.
Which version should I pick? Whichever you actually play. The four builds have different horses and data, and nothing carries across, so the wrong version gives the wrong answers.
Where do my .card files come from? The Stable Management System creates and saves them, and the home game saves your horses as cards. Older horses may be .raw; every tool reads both.
Is it really free? Yes. It is shared for preservation and for the community. The tools are open source; the game itself is not hosted here, and there is a short note on the site explaining why.