Masters Games or Online Games: Which Database Should You Trust?

Two different worlds

Every opening explorer offers a choice of source. Most people pick one on the first day and never think about it again, which is a shame, because it changes the answer to almost every question you ask.

Master games are over the board games between titled players. A few million of them, played slowly, by people who have prepared.

Online games are blitz and rapid, in the hundreds of millions, played by everyone.

The shapes are completely different. In master games one move usually dominates, because strong players converge on the best move. In online games the replies spread out, because the population contains every level of understanding.

Which one you should use

The rule is short: prepare against the database that looks like your opponents.

If you play online rapid at 1500, the master database is describing games you will never have. Preparing against it means learning answers to moves nobody at your level plays, while remaining unprepared for the moves they do.

If you are preparing for a specific tournament opponent rated 2100 over the board, the online database is too noisy to help.

For most people reading this that means online games, filtered to a rating band near your own. It is the single most consequential setting in an opening explorer and the one almost nobody changes.

What each one hides

Master games understate mistakes. They are a picture of best play. Exactly what you want when deciding whether a line is sound, and exactly what you do not want when deciding what to expect.

Online games overstate speed. Mostly fast games, so they reflect what people play under time pressure. Natural quick moves are over-represented and moves that need calculation are under-represented, even when they are better.

Both carry survivorship. A line that stopped being played five years ago disappears from recent data whether it was refuted or simply went out of fashion.

Using both

Ask each database the question it is good at.

Use masters to decide whether a line is sound. If strong players have abandoned a variation, that is worth knowing before you build a repertoire on it.

Use online games at your band to decide what to prepare first. The frequency column there is a forecast of your next month of games.

Together they answer the question that actually matters: what will I face, and is my answer to it any good.

A worked habit

When you add a line, check it twice.

Once against masters, to confirm the move you chose is respectable. Once against online games at your band, to see how often you will need it. If the second number is tiny you have found something to cut, which is covered in when to prune a repertoire.

In Chess Prep Pro the source and rating band are settings on the opening book, and the same settings drive the repertoire scans, so what the book calls common is what the app calls a gap.