---
title: "Sideline in chess"
url: "https://georgelichess.com/glossary/sideline.md"
canonical_url: "https://georgelichess.com/glossary/sideline"
last_updated: "2026-11-07"
type: "reference"
summary: "A sideline is a less common or less critical branch of an opening that is considered playable. The alternatives are sidelines."
related: ["https://georgelichess.com/glossary/main-line.md", "https://georgelichess.com/glossary/opening-theory.md", "https://georgelichess.com/glossary/opening-repertoire.md", "https://georgelichess.com/glossary/trap-in-the-opening.md", "https://georgelichess.com/glossary/category/opening-concepts.md", "https://georgelichess.com/glossary.md"]
---

# Sideline in chess

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A sideline is a less common or less critical branch of an opening that is considered playable. The alternatives are sidelines.

A sideline is a less common or less critical branch of an opening that is considered playable but is not the move most often chosen at the highest level of theory.

Every [opening](https://georgelichess.com/glossary/opening.md) has a [main line](https://georgelichess.com/glossary/main-line.md), the sequence most players choose, and a number of alternatives. The alternatives are sidelines. They may be perfectly sound, but they are met less often and are usually less deeply analyzed.

Players choose sidelines for practical reasons. A sideline can take the opponent out of their preparation, lead to a type of position the opponent dislikes, or simply be easier to learn because there is less [theory](https://georgelichess.com/glossary/opening-theory.md) to remember. A sound sideline played with understanding can score very well against opponents who only know the main line.

The cost is that a sideline often gives the opponent an easier or safer route to equality, since the most testing play has been left aside. Some sidelines are also hiding places for traps that work only against an unprepared opponent.

When learning an opening, start with the ideas of the main line, then add a sideline you can actually play. A common [mistake](https://georgelichess.com/glossary/mistake.md) is to pick a sideline for its tricks and not learn the plan behind it, so that a well prepared opponent meets the trap with the right answer and leaves you with a worse position.

Compare it with [Italian setup](https://georgelichess.com/glossary/italian-setup.md). The Italian setup is a White formation after e4 and Nf3 with the bishop on c4 aimed at f7, usually supported by c3 and d3, used for a patient fight in the center and on the kingside.

Also worth reading is [Opponent preparation](https://georgelichess.com/glossary/opponent-preparation.md). Opponent preparation is the work of studying a known opponent's past games and habits before a round so you can choose openings and plans that steer the game toward positions where they are less comfortable.

Whether "Sideline" suits your repertoire depends on the games you play. A [first lesson](https://georgelichess.com/book/first-lesson.md) with George Li maps what you play today and what to build next.

## Related terms

- [Main line](https://georgelichess.com/glossary/main-line.md)
- [Opening theory](https://georgelichess.com/glossary/opening-theory.md)
- [Opening repertoire](https://georgelichess.com/glossary/opening-repertoire.md)
- [Trap in the opening](https://georgelichess.com/glossary/trap-in-the-opening.md)

## Guides that go further

- [Most popular chess openings and win rates](https://georgelichess.com/chess-opening-statistics.md): The most played openings, how often White wins, and how the numbers change with rating, computed from public games.
- [How to choose a chess coach](https://georgelichess.com/how-to-choose-a-chess-coach.md): What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
- [The first lesson](https://georgelichess.com/book/first-lesson.md): A game review, a read on your level and a written study plan from George Li.

[Book your first lesson](https://georgelichess.com/book.md) and George Li reviews your games and builds a study plan around them. Questions about lessons: write to hello@georgelichess.com.

## Related

- [Main line in chess](https://georgelichess.com/glossary/main-line.md)
- [Opening theory in chess](https://georgelichess.com/glossary/opening-theory.md)
- [Opening repertoire in chess](https://georgelichess.com/glossary/opening-repertoire.md)
- [Trap in the opening in chess](https://georgelichess.com/glossary/trap-in-the-opening.md)
- [Chess terms: Opening concepts](https://georgelichess.com/glossary/category/opening-concepts.md)
- [Chess terms glossary: plain definitions](https://georgelichess.com/glossary.md)