How-to guide · how to purge unused blocks in autocad

How to purge unused blocks in AutoCAD

DWGDXFFree1,223 words

By Sumana Kumar · Published 17 Jun 2022 · Updated 17 Apr 2024

Drawings accumulate clutter. Every time you insert a block and later delete every instance, the block's definition stays behind in the drawing's block table, invisible but taking up space. Copy and paste between files, adopt a downloaded library, or import a consultant's DWG, and you drag in dozens of definitions you never use. PURGE is the command that sweeps all of that out, removing unreferenced block definitions — along with unused layers, linetypes, text styles and more — to leave a lean, fast drawing.

This guide shows how to purge unused blocks safely, how to reach the stubborn items that resist a single purge, and how PURGE fits into a broader drawing-cleanup routine that can dramatically shrink a bloated DWG. It also explains the difference between an unused definition and a placed instance, so you never delete something you actually need.

The golden rule: PURGE only ever removes definitions that are not used anywhere. A block you have placed in the drawing is safe — only the orphaned, unreferenced definitions go.

Step 1 — Open the Purge dialog

Type PURGE (or PU) and press Enter to open the Purge dialog. It shows a tree of named objects that can be removed — blocks, layers, dimension styles, text styles, linetypes, materials and more — with the purgeable items listed under each. Expand 'Blocks' to see every unused block definition the drawing is currently carrying.

Tick 'Purge nested items' so that definitions only used by other unused definitions get cleared too — without it, a block nested inside another unused block can hang on. It is also worth ticking the option to confirm each purge while you learn what is being removed; once you trust it, you can purge in one pass. The dialog is non-destructive to anything in use, so you can explore it freely.

Step 2 — Purge the unused blocks

In the Blocks branch, select the block definitions you want to remove — or select the whole Blocks node to clear them all — and click 'Purge'. Confirm if prompted. The unreferenced definitions vanish from the block table. You can also click 'Purge All' to sweep every category at once: unused blocks, layers, styles and the rest in a single action, which is the usual move for a general cleanup.

Nothing you have actually placed is touched — PURGE refuses to remove a block that has even one instance in the drawing. So purging is safe to run liberally. If you are unsure, run it, then check the drawing; you will find the visible content unchanged and the block list shorter.

Step 3 — Run it more than once

Purging often needs a couple of passes. Block definitions can be nested — block A contains block B — so deleting A's last instance leaves A purgeable, but B only becomes purgeable once A is gone. The first purge removes A; a second purge then catches B. Even with 'Purge nested items' ticked, running PURGE two or three times until it reports nothing left to purge is good practice.

Think of it as peeling layers: each pass exposes the next set of now-orphaned definitions. When a run of PURGE finds nothing to remove, the drawing's block table is genuinely clean. This repeated-pass habit is the single most-missed step, and it is why a drawing that 'won't get smaller' often just needs purging again.

Why a block won't purge

Sometimes a block you are sure is unused refuses to purge, and there are specific reasons. The most common is a lingering instance somewhere you can't see — on a frozen or off layer, far outside the visible area, or inside another block. Run ZOOM Extents and check every layer is thawed and on, then look again; a single hidden instance keeps the definition alive. The COUNT or QSELECT methods can confirm whether any instances really remain.

Other blockers: a block referenced by a dynamic block, a tool palette, or a field will resist purging. Anonymous blocks used by hatches and dimensions are managed internally and won't purge while those objects exist. And a definition referenced from a 'multiple insert' (MINSERT) object stays until that object is removed. Track down and delete the last real reference, and the definition will purge on the next pass.

Purge as part of shrinking a bloated DWG

Purging unused blocks is the centrepiece of slimming a heavy drawing, but it works best alongside a few companions. Run OVERKILL to delete duplicate and overlapping geometry that inflates the file and corrupts counts. Run AUDIT to find and fix errors in the drawing database, and RECOVER on a file that is misbehaving. Detach any external references you no longer need before purging. Then PURGE All, repeated until clean.

For the most dramatic reduction, WBLOCK the whole drawing out to a new file: select everything (or use the '*' entire-drawing option), and AutoCAD writes a fresh DWG that contains only what is actually used, leaving every scrap of unreferenced baggage behind. A drawing that ballooned through months of copy-paste editing can drop sharply in size after a purge-and-WBLOCK pass, opening and saving faster for everyone who touches it.

When NOT to purge — keeping a working library

There is one situation where you deliberately do not purge: when a drawing is acting as a block library or template. If you keep a DWG full of standard blocks ready to be inserted into projects, those definitions are 'unused' in that file by design — they exist precisely so they can be copied out. Purge it and you wipe your library.

So before a blanket PURGE All, ask what the drawing is for. A production sheet should be purged hard to stay lean. A library or template file should keep its unplaced definitions. If you want a clean production drawing but also a stash of those handy blocks, WBLOCK the blocks you want to keep into a separate library file first, then purge the working drawing freely. That way you get the lean sheet and never lose the kit you built up.

Free download

Browse the full library — DWG & DXF, no signup.

Download CAD blocks

Questions

Frequently asked

Does purging delete blocks I'm actually using?+

No. PURGE only removes block definitions that have no instances placed anywhere in the drawing. Any block you have inserted — even once, even on a frozen layer — is protected and won't be purged. Only orphaned, unreferenced definitions are removed.

Why won't a particular block purge?+

There's almost always a hidden instance keeping it alive — on a frozen or off layer, far outside the view, or nested inside another block. Thaw and turn on all layers, run ZOOM Extents, and check with COUNT or QSELECT. Blocks referenced by dynamic blocks, MINSERT objects or fields also resist purging.

Why do I have to run PURGE several times?+

Blocks can be nested. Removing the last instance of an outer block makes it purgeable, but a block nested inside it only becomes purgeable once the outer one is gone. Run PURGE repeatedly — even with 'Purge nested items' ticked — until it reports nothing left to remove.

Will purging unused blocks make my DWG smaller?+

Yes, often substantially, especially in files bloated by copy-paste editing or imported libraries. For the biggest reduction, combine PURGE with OVERKILL and AUDIT, then WBLOCK the whole drawing to a new file, which writes out only the content actually in use.

Related downloads