BlockCompare

How BlockCompare works

These are the tabs inside the actual app, in the order they appear — every screenshot below is a real, unedited capture of BlockCompare running.

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Tab: Select Files

Step 1 — Add the before and after revisions

Point BlockCompare at two folders — the drawings before a change and the same drawings after — and narrow down which blocks, layers or viewports actually matter before scanning. A Compare DWG / Compare with Excel switch in the title bar picks between that two-folder workflow and comparing against an exported Excel workbook instead.

1. 1Use the Compare DWG / Compare with Excel switch in the title bar first — Compare DWG (the default, described below) reads both sides from disk; Compare with Excel swaps Folder A for a single block-data workbook exported by the companion BlockSync tool, while Folder B stays a live folder of DWGs.
2. 2Add Files or Add Folder into Folder A (before) and Folder B (after) — any number of DWGs on each side.
3. 3BlockCompare pre-scans both folders and reports a live status per file before comparison begins.
4. 4Open the Blocks tab to check exactly which block definitions to compare — each row shows its reference count, how many files contain it, whether it's dynamic, and whether it has attributes at all.
5. 5Switch to the Layers or Viewports tab to narrow the comparison to specific layers or paper-space viewports instead of the whole drawing.
6. 6Pick a Match strategy — Filename priority, Handle priority, or Hybrid (default, weighted toward handle matches) — and drag the Confidence threshold slider that decides how sure a file pairing has to be before it's proposed automatically.
7. 7Save the current tab selections as a named Filter profile (Save…) and reload it later (Load) for a recurring comparison job on the same project.
8. 8Click Scan & Match to read every file and propose file-to-file pairings.

Options on this screen

Filename priority / Handle priority / Hybrid (default)

Which signal to trust more when pairing a 'before' file to its 'after' counterpart. Hybrid blends both, weighted toward the handle match.

Confidence threshold

How confident a proposed file pairing has to be before BlockCompare accepts it automatically instead of flagging it for manual review.

Compare DWG / Compare with Excel

Compare with Excel narrows Folder B's scan to just the block names found in the workbook and defaults to Filename priority matching, since the workbook's recorded file names — not live handle data — are the more reliable signal on that side.

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Tab: Review Matches

Step 2 — Confirm or correct the proposed file pairings

BlockCompare pairs each 'before' file to its most likely 'after' counterpart automatically — this screen is where you confirm that, or fix it by hand, before anything is compared.

1. 1Each row lists File A next to BlockCompare's proposed File B, with a Filename %, Handle % and Combined % score showing how confident the match is.
2. 2Rows highlighted in red are conflicts — the filename and handle signals disagree — and list a Conflict candidate so you can see the runner-up before deciding.
3. 3Override any proposed match with the File B dropdown, or tick Exclude to drop a file from the run entirely.
4. 4Change Strategy and click Re-match at any point to re-run the pairing algorithm against the current file lists.
5. 5Click Compare once every pairing is confirmed.

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Tab: Comparison Report

Step 3 — Review exactly what changed, block by block

Every matched pair is compared by AutoCAD's persistent object handle, so a block that moved, got reattributed, or changed layer is reported precisely — never just flagged as 'different'.

1. 1Results are grouped per matched file pair, each with a summary line and an expandable list of entries.
2. 2Every entry shows its Handle, Block Name, Kind (Added / Removed / Modified) and how many Fields Changed.
3. 3Click Details… on any modified entry to open a popup listing every changed field's Old Value and New Value side by side.
4. 4Unchanged block instances aren't listed at all, so a drawing with thousands of instances doesn't bury the handful of real differences.
5. 5Click Finish to close out the session, or Back to adjust the match and re-compare.

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Tab: Export to Excel

Hand the report to someone who doesn't have BlockCompare

The same Added / Removed / Modified breakdown, with every field-level change, written to a workbook that anyone can open, filter or archive — in either of two layouts you pick at export time.

1. 1From the Comparison Report screen, click Export to Excel, then choose a report layout in the dialog that appears.
2. 2The workbook lists every changed, added and removed block instance with its file pairing, handle, block name, and field-level old/new values.
3. 3As a flat, filterable spreadsheet it works as a review artifact or a QA sign-off record without anyone needing BlockCompare installed.

Options on this screen

One row per record (default)

Every instance gets a single row; a changed field's old value is left as a comment on the cell, so the sheet stays compact.

Before/after rows for changed records

A Modified instance instead gets two adjacent rows — one with the old values, one with the new — and every field that actually changed is highlighted on both rows, so old and new sit side by side without hovering a comment.

Environment & requirements

Everything that determines whether BlockCompare will run on your machine, and how it behaves once it does.

• No Microsoft Excel installation required — BlockCompare reads and writes .xlsx directly with its own engine (ClosedXML).
• Windows 10/11, 64-bit only.
• Requires a licensed, full version of AutoCAD (2021–2027). AutoCAD LT is not supported — LT can't run the background automation BlockCompare depends on.
• If more than one AutoCAD version is installed, pick which one to use under Settings → AutoCAD, or leave it on "Auto (newest installed)" — if that version fails to load for any reason, it falls back to another installed version automatically.
• Built on .NET 8. If the .NET 8 Desktop Runtime isn't already on your machine, the installer prompts to fetch it from Microsoft (free, one-time, roughly 60 MB).
• Network access is used only to check your license at startup and periodically afterward. Scanning, reading and writing all happen locally through AutoCAD's own engine — no drawing content is ever uploaded.
• Interface language: English.
• Batches of many files can process several drawings in the background in parallel — tune "Max parallel AutoCAD instances" in Settings to trade speed for CPU/memory headroom.
• Every long-running action shows a progress bar with a percentage and estimated time remaining, and can be canceled mid-run.
• Settings → Diagnostics → Open Log Folder gets you straight to the host and plugin logs if something needs troubleshooting.

See also the site-wide system requirements page comparing all tools.