Merge vs Rebase

🤔 What’s the Difference?

Both merge and rebase combine changes from one branch into another — but they do it very differently.

Merge creates a new commit that ties two histories together. Rebase replays your commits on top of another branch, creating a linear history.

flowchart TB
    subgraph Merge[Merge]
        direction LR
        M1[main: A → B → C] --> M2[Merge commit]
        M3[feature: D → E] --> M2
        M2 --> M4[Linear + merge commit]
    end

    subgraph Rebase[Rebase]
        direction LR
        R1[feature: D → E] --> R2["Rebased: D' → E'<br/>(replayed on top of C)"]
        R3[main: A → B → C] --> R2
        R2 --> R4[Perfectly linear]
    end

    style Merge fill:#3b82f6,color:#fff
    style Rebase fill:#f59e0b,color:#fff
    style M2 fill:#10b981,color:#fff
    style R2 fill:#10b981,color:#fff

Visual timeline:

Merge:
main:    A ──▶ B ──▶ C ──────────▶ F (merge commit)
                      \           /
feature:               D ──────── E

Rebase:
main:    A ──▶ B ──▶ C
                      │
feature:              ├─▶ D' ──▶ E' (replayed, new hashes)
(original D and E are discarded)

🔄 How Rebase Works

# Current situation: feature branch is behind main
git switch feature
git rebase main

# What happens step by step:
# 1. Git finds the common ancestor (commit where feature branched off)
# 2. Git temporarily sets aside feature's commits (D, E)
# 3. Git moves feature to point to main's tip (C)
# 4. Git replays D and E on top of C → D' and E' (new commits with new hashes)

📋 Command Comparison

# MERGE — keeps all history
git switch main
git merge feature

# REBASE — rewrites history
git switch feature
git rebase main
git switch main
git merge feature    # now a fast-forward!

⚠️ The Golden Rule of Rebase

Never rebase commits that have been pushed to a shared branch.

If you rebase a branch that others are working on, their local copies will have different commit history. It’s like rewriting history in a shared textbook — chaos ensues.

Safe to rebase: ✅ Your local feature branch (never pushed) Never rebase: ❌ main, develop, or any branch others have pulled from

🎯 When to Use What

Use Merge when…	Use Rebase when…
You want to preserve exact history	You want a clean, linear history
Working on a shared branch	Working on a local feature branch
You want to see when branches diverged	You want to avoid merge commits
Collaborating with a team	Updating your branch with latest main

In Simple Words

Merge creates a commit that ties two branches together (preserves history)
Rebase replays your commits on top of another branch (linear history)
Golden rule: Never rebase commits you’ve already pushed to a shared branch
Merge is safer for collaboration; rebase gives cleaner history
After rebasing, you can fast-forward merge into main for a straight line