Download v1.2.0 Free  ·  Chrome  ·  2 min install

The data Ancestry has.
Now visible where you work.

Every match on your list comes with match statistics Ancestry already knows but doesn't show you. This extension puts that information where it belongs: right there in the list, without any extra clicking.

What Ancestry shows you
Rebecca Landau · 54 cM · 4 segments 🌳
2nd–3rd cousin · Linked tree
Morris Blumstein · 38 cM · 4 segments
3rd–4th cousin · No linked tree
Esther Kaplan-Friedman · 29 cM · 9 segments 🌳
3rd–4th cousin · Linked tree
Yosef Bernstein · 47 cM · 3 segments
2nd–3rd cousin · No linked tree

Why two matches that look the same aren't.

Both of these fictional matches share 135 cM. Ancestry shows them identically. One of them is worth your time. The other probably isn't. Here's how you can tell the difference at a glance.

Ancestry — without DNA+
Distant Family
M
Match A
Half 3rd cousin or 3rd cousin 1x removed
Unassigned
135 cM | 2% shared DNA
Public linked tree
48 people
+ Add
···
R
Match B
Half 3rd cousin or 3rd cousin 1x removed
Unassigned
135 cM | 2% shared DNA
Public linked tree
23 people
+ Add
···
Same page — with DNA+ Segment Detector
DNA+
2 matches loaded
unweighted cM · longest segment · AScM
Distant Family
M
Match A
Half 3rd cousin or 3rd cousin 1x removed
Unassigned
135 cM | 2% shared DNA
TOTAL CM 135
SEGMENTS 15
Longest 9 cM ✗ AScM 9.0 ✗
Public linked tree
48 people
+ Add
···
R
Match B
Half 3rd cousin or 3rd cousin 1x removed
Unassigned
135 cM | 2% shared DNA
TOTAL CM 135
SEGMENTS 8
Longest 25 cM ✓ AScM 16.9 ✓
Public linked tree
23 people
+ Add
···

Same total DNA. Completely different picture.

Both matches share 135 cM, but the breakdown tells two very different stories.

The numbers
Total cM Segments Longest AScM
Match A 135 15 9 cM ✗ 9.0 ✗
Match B 135 8 25 cM ✓ 16.9 ✓
Match A

135 cM spread across 15 tiny pieces. No single piece is long enough to point to a traceable ancestor. The total looks meaningful, but this pattern is common in Ashkenazi research and rarely leads anywhere useful.

Match B

Also 135 cM, but across only 8 segments, with the longest at 25 cM. Fewer, larger blocks like these almost always trace back to a specific ancestor you can actually find.

About AScM (Average Segment Size, cM)
Total shared cM divided by number of segments. A higher number means the DNA is concentrated in fewer, larger blocks. Lower means it is scattered across many small fragments, typical of deep Ashkenazi endogamy background rather than a traceable recent connection.
16.9 ✓ Strong signal Large blocks. Likely a meaningful, traceable connection. Prioritize these.
11.1 ~ Worth a look Pursue green matches first. Come back when something else lines up.
9.0 ✗ Background noise The DNA is real, but likely reflects ancient shared ancestry rather than a traceable link.
Ancestry shows both rows the same way. DNA+ Segment Detector shows you the difference.
Match A and Match B are fictional examples. No real names or data are used.

What the colors mean

Each match gets two badges — one for longest segment, one for AScM. You don't need to know what those terms mean to use them. Green means worth your time. Red means set it aside for now. Yellow means keep an eye on it but don't prioritize it.

Longest 27 cM ✓ AScM 15.3 ✓
Both green — start here. Strong numbers on both counts — this is the match to open first.
Longest 22 cM ✓ AScM 11.0 ~
One green, one yellow — worth a second look, especially if the longest segment is strong.
Longest 11 cM ✗ AScM 3.8 ✗
Both red — real DNA, but too scattered to be traceable right now. Move on.

Your thresholds, your call

DNA+
Segment Detector
Research Thresholds
Longest segment cM
−
20
+
AScM minimum
−
12
+
v1.2.0  ·  © 2026 David Wilbur

The defaults — longest segment 20 cM, AScM 12 — reflect the working consensus for Ashkenazi Jewish genealogy research. They're a reasonable starting point for most testers.

If you want to be more selective, raise them. If you're casting a wider net on a specific line, lower them. The badges across your entire match list update immediately when you save.

Nothing leaves your browser

Ancestry already has this data — it comes back from their servers every time you load a match. The extension reads what's already there and displays it in front of you. Nothing is collected, stored, or sent anywhere. No account, no setup, no separate login.

Get DNA+ Segment Detector

Not on the Chrome Web Store — this is a private release, shared directly. It takes about two minutes to install, and you only have to do it once.

DNA-Segment-Detector-v1.2.0.zip
Free  ·  Chrome Extension  ·  v1.2.0  ·  Developer Mode install
Download Free
How to install  ·  about 2 minutes
1
Download and unzip

Save DNA-Segment-Detector-v1.2.0.zip and unzip it. You'll get a folder with a few files inside — manifest.json, content.js, and a couple more.

2
Open Chrome's extension page

In Chrome, go to chrome://extensions — just paste that into the address bar.

3
Turn on Developer Mode

Flip the toggle in the top-right corner of that page. It sounds more serious than it is — it's a standard Chrome feature, no special access needed. You can turn it back off after if you prefer.

4
Load the extension

Click Load unpacked, then select the folder you unzipped in step 1. That's it.

5
Go to Ancestry and look up

Navigate to your DNA match list. The DNA+ toolbar will be waiting there for you.

Updating later: repeat steps 4–5 with the new folder, then hit the refresh icon on the extension card at chrome://extensions.