Differential Backup Vs Incremental Backup.

By / Computer Backups / 6 minutes of reading

What they are, how they differ, and which one to use on your home PC?

If you’ve ever set up a backup program and spotted the words “differential” or “incremental” in the options, you might have wondered what on earth they mean — and whether it matters. It does. Choosing the wrong type can fill up your backup drive surprisingly fast, or leave you with a harder recovery job if something goes wrong.

This guide explains all three backup types in plain English, so you can make the right choice for your home PC.

Table Of Contents
  1. The Three Types of Computer Backup
  2. How Differential Backups Work
  3. How Incremental Backups Work
  4. Differential vs Incremental: Side-by-Side Comparison
  5. The Grandfather, Father, Son Backup Strategy (GFS)
  6. Frequently Asked Questions

The Three Types of Computer Backup

Almost every backup program out there — whether you use Macrium Reflect, Acronis, EasUS Todo, or another tool — offers three fundamental backup types.

Type 1

Full Backup

Copies everything: your operating system, apps, settings, and all your files. The starting point for any backup strategy.

Type 2

Differential Backup

Copies only what has changed since your last full backup. Gets bigger every day, but restoring is simple.

Type 3

Incremental Backup

Copies only what has changed since any previous backup. Stays small, but you need every piece to restore.

Note

You always need at least one full backup before differential or incremental backups can work. Think of the full backup as the foundation or the starting point, and the others as updates layered on top of it.

How Differential Backups Work

After your initial full backup, a differential backup asks: “What has changed since that full backup?” It then copies only those changed files.

The key word is since. Each differential backup looks back at the full backup — not at yesterday’s differential — which means every differential contains all the changes from day one up to today.

Differential backups grow over time. On day 1, a differential might be 2 GB. By day 30, it could be 40 GB or more — even larger than your original full backup if you’re not careful.

This is because each differential repeats files that were already included in the previous differential. There’s a lot of duplication. For this reason, it’s good practice to run a fresh full backup every few weeks to “reset” the clock.

How Differential Backup Size Grows

Full

Full

120 GB

Week 1

Full

Diff

+ 4 GB

Week 2

Full

Diff

+ 10 GB (and growing)

Week 3

Full

Diff

+ 18 GB (and growing)

Differential backups always refer back to the last Full Backup. They completely ignore any other type of backup. What that means is that files included in the first differential backup will also be included in the second and the third and so on. That creates a lot of duplication which in turn uses up space on your backup device.

How Incremental Backups Work

After your initial full backup, a differential backup asks: “What has changed since that full backup?” It then copies only those changed files.

The key word is since. Each differential backup looks back at the full backup — not at yesterday’s differential — which means every differential contains all the changes from day one up to today.

Differential backups grow over time. On day 1, a differential might be 2 GB. By day 30, it could be 40 GB or more — even larger than your original full backup if you’re not careful.

This is because each differential repeats files that were already included in the previous differential. There’s a lot of duplication. For this reason, it’s good practice to run a fresh full backup every few weeks to “reset” the clock.

How Incremental Backup Sizes Stay Small

Full

Full

120 GB

Day 1

Full

Inc

+ 1.2 GB

Day 2

Full

Inc

Inc

+ 0.8 GB (and growing)

Day 3

Full

Inc

Inc

Inc

+ 1 GB (and growing)

Incremental backups are the most storage-efficient option. That’s because there’s no duplication of files in the backups. Incremental backups can run for a long time and still produce consistently small file sizes. If your backup drive is running low on space, switching from differential to incremental can dramatically extend how long it lasts.

Differential vs Incremental: Side-by-Side Comparison

FeatureDifferentialIncremental
What gets backed upChanges since the last full backupChanges since the last backup of any type
Backup file sizeGrows over timeStays consistently small
Storage space usedModerate to highLow
Speed to back upSlower as time goes onFast — only today’s changes
Files to restore fromFull backup + latest differential (2 files)Full backup + every incremental (many files)
Restore speedFasterSlower
Risk if one backup failsLower — others overlapHigher — chain can break

Restoring your computer

This is where the real difference between differential and incremental backups becomes clear.

Differential

You only need two things: the original full backup, plus the most recent differential backup. That’s it. Load both, and your restore is complete. Simple.

Incremental

You need the full backup plus every single incremental in the chain, in order. If you’ve been running daily incrementals for three weeks, you need the full backup plus 21 incremental files — all intact, all in sequence.

What Happens if a Backup File is Damaged?

This is the hidden risk of incremental backups. Because each increment only contains what changed on that specific day, if one file in the chain becomes corrupted or goes missing, you can lose everything that came after it — even if all the other files are perfectly fine.

Differential backups carry less of this risk. Because each differential repeats everything since the full backup, the files overlap quite a bit. If Monday’s differential fails, Tuesday’s likely contains most of Monday’s data anyway.

If you use incremental backups, it’s especially important to verify them regularly and to run a fresh full backup every few weeks to shorten the chain.

The Grandfather, Father, Son Backup Strategy (GFS)

Many years ago the grandfather, father, son (GFS) backup strategy was developed to combine the strengths of both differential and incremental backups while negating their respective weaknesses.

  • Grandfather – A full backup taken monthly.
  • Father – Differential backups taken weekly
  • Son – Daily incremental backups.

Using the GFS system you’ll create a monthly “backup set”. Then at the start of the second month a new set will begin with the creation of a new full backup.

Each backup set contains a lot of duplication of files to protect against corruption or damage while still making best use of the available space on your storage drive.

Typically, on a home computer, you’d be looking to keep 3 sets, which would allow you to “go back” 3 months. At the beginning of the fourth month the oldest backup set would be deleted.

Backing Up Your Windows PC

There are many ways in which you could create backups of your home computer. If you’re still using Windows 10, you could use the built in Backup and Restore tool. This tool creates a full system image of your PC.

The advantages of this is that it’s already installed on your computer and it easy to use. The disadvantage is that it only creates system images, you don’t have any other options and by default it’ll overwrite the last system image so you can only ever have one backup, but there are ways around this How To Store Multiple Windows System Images On A Single Drive.

Microsoft explicitly don’t recommend Back and Restore for Windows 11 (although it is still installed). Instead they recommend that you use a third party tool instead. If you’re searching for free option then EaseUS Todo works well and is easy to use Windows 11 Backup

Frequently Asked Questions

Setup a Home Network in Windows

Setting up a home network in Windows 10 or Windows 11 lets you share files and folders between all your desktop PCs and laptops

Access documents, pictures and any other files that are stored on a different PC to the one you’re using right now.

Click Here
How to setup a home network in Windows 10 and Windows 11. 5 Simple steps.

Find this and other related guides in – Computer Tech Guides – Windows 11 – Windows 10

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