DNA Chromosome Browser: What It Is and How to Use One
When you first open your DNA match list, you are greeted with a list of names and estimated relationship ranges based on the total amount of shared DNA. But while knowing you share 150 cM with a match is helpful, it doesn’t tell you how you are related, or which ancestor passed that DNA down to you. To answer those questions, you must peer beneath the surface and analyze your raw segment data. An online chromosome browser is the ultimate tool to visualize genetic inheritance, trace shared segments on Chromosomes 1 through 22, and systematically map your family tree.
Humans carry 23 pairs of chromosomes. Pairs 1 through 22 are autosomes, which are inherited randomly from both your mother and father and are analyzed for cousin matching. The 23rd pair determines your biological sex (X/Y). A chromosome browser displays your autosomes as 22 horizontal bars, mapping exactly where you and your genetic matches share identical blocks of DNA.
What is a Chromosome Browser?
A chromosome browser is a visual rendering tool provided by leading DNA databases that displays a schematic map of your chromosomes. Instead of showing you just a numeric estimate of shared DNA, it plots the physical segments of matching DNA as colored blocks along Chromosomes 1 through 22.
When you select a match to compare against your profile, the browser lines up your chromosomes side-by-side. If the browser detects a shared segment—meaning an identical sequence of genetic markers—it “paints” that segment on the corresponding chromosome bar. By visualizing these blocks, you can see exactly where your matches overlap and start grouping matches who share the same physical segments.
How Do Chromosome Browsers Work?
To use a chromosome browser effectively, you must understand the three core metrics used to measure shared DNA segments:
- Centimorgans (cM): This is the unit of genetic measurement representing the probability of recombination. A larger shared cM value (e.g., 45 cM vs. 8 cM) indicates a longer, more reliable physical segment and a closer biological relationship. Learn more in our guide on how DNA matching works.
- Segment Count: The total number of distinct blocks of shared DNA. Close relatives share many large segments across multiple chromosomes, while distant cousins might only share a single small segment on one chromosome.
- Longest Segment (cM): This is the single most important metric for filtering distant matches. Because small segments can be inherited unchanged over many generations, a match with 30 cM shared across 3 segments might actually be a false match if their longest segment is only 6 cM. A high longest segment (e.g., 18+ cM) strongly supports a recent common ancestor.
To avoid wasting time chasing false matches, most veteran genetic genealogists use a **7 cM to 10 cM threshold cutoff**. Segments smaller than 7 cM have a high probability of being “identical by state” (IBS)—meaning they are identical by random chance or represent ancient population-wide DNA, rather than a genealogically traceable common ancestor. Focus your initial segment mapping exclusively on matches with at least one segment of 10 cM or larger.
Chromosome Browser Setup & Tips by Platform
While the underlying genetics are identical, each commercial database has its own interface, tools, and unique features. Here is how to configure and leverage chromosome browsers on the major platforms:
1. MyHeritage DNA
MyHeritage offers one of the most intuitive and visually rich chromosome browsers in the industry. It is natively integrated into their match profiles and supports both one-to-one and one-to-many comparisons.
- How to Set It Up: Go to your DNA Match list, select a match, and scroll down to the bottom of their profile to find the browser. To compare multiple people, go to the main menu and select DNA -> Chromosome Browser, where you can select up to 7 matches simultaneously.
- Unique Feature — Shared Matches Triangulation: When comparing multiple matches, MyHeritage will automatically highlight triangulated segments with a **bracket/halo outline**. If a segment is highlighted, it proves that you, Match A, and Match B all share that exact chromosomal segment, indicating a shared ancestral couple.
2. FamilyTreeDNA (FTDNA)
FamilyTreeDNA was the pioneer of commercial chromosome browsers. Their interface is highly detailed and allows you to compare up to 5 matches at once.
- How to Set It Up: Log into your FTDNA dashboard, select Chromosome Browser from your Autosomal results menu. Select the matches you wish to compare from your list on the left, and click Compare.
- Specialist Tip: FTDNA allows you to download your shared segment data as a CSV file. This is highly useful for copying segment data into your offline chromosome mapping logs or spreadsheets. You can get our specialized spreadsheets on our free templates hub.
3. GEDmatch
GEDmatch is the playground of advanced genetic genealogists. It is a free third-party portal that allows you to upload raw DNA data from any company to compare segments with researchers across database walls.
- How to Set It Up: After uploading your raw zip file, use the One-to-One Autosomal Comparison tool. Input your kit number and your match’s kit number to render a highly detailed segment-by-segment graphic.
- Granular Settings: Unlike commercial platforms, GEDmatch allows you to adjust the minimum segment size (cM) and SNP threshold. If you suspect endogamy, you can raise the cM limit to 10 or 15 cM to filter out noise, or lower it to 5 cM for targeted, close-range verification.
4. AncestryDNA Workaround
AncestryDNA holds the largest cousin matching database in the world (over 25 million testers) but **does not provide a chromosome browser or segment data** on their platform due to their strict corporate privacy standards.
The Workaround: You cannot map segments directly on Ancestry. However, you can download your raw DNA file from Ancestry for free, and then upload it to **MyHeritage, FamilyTreeDNA, and GEDmatch**. By encouraging your most important Ancestry matches to do the same, you can compare their segments inside those open databases. Learn the step-by-step raw data migration process in our DNA transfer strategy guide.
Understanding Chromosome Mapping & Segment Painting
When a browser paints a segment of shared DNA, it is showing you a region on one of your chromosome pairs. But remember: you have **two physical chromosomes** for each numbered pair (one from your mother, one from your father). Standard autosomal chromosome browsers cannot tell which side of the pair a segment belongs to—this is known as “unphased” segment data.
To map your chromosomes to specific ancestors, you must group your matches into maternal and paternal branches. By comparing maternal-side cousins, you can identify segments inherited from your mother’s ancestors. Over time, you can paint a complete visual map of your genome, coloring specific chromosomal regions by the ancestral couples who passed them down. To begin, use our free client-side DNA Chromosome Browser and log your segments in our custom Chromosome Mapping Excel templates.
Not all matching DNA segments represent a traceable family tree connection. Some areas of the human genome contain **”pile-up” regions**—highly conservative segments of DNA where mutations rarely occur. Because these regions are preserved unchanged for hundreds of years, you may share a 10 cM segment in a pile-up region with thousands of people with whom you share no recent genealogical ancestors. Always cross-reference your segment mapping against known pile-up lists (like those on Chromosomes 6, 9, and 15) to avoid grafting false branches onto your tree.
Chromosome Browser Platforms Comparison
| Platform | Max Comparisons | Auto-Triangulation | Raw Uploads | Segment Downloads |
|---|---|---|---|---|
| MyHeritage DNA | 7 Matches | ✅ Yes (Halo Brackets) | ✅ Yes ($19 Unlock) | ❌ No (Manual Copy) |
| GEDmatch | Limitless (Tier 1) | ✅ Yes (3D Matrices) | ✅ Yes (100% Free) | ✅ Yes (Detailed CSV) |
| FamilyTreeDNA | 5 Matches | ❌ No | ✅ Yes (Free Matches) | ✅ Yes (CSV download) |
| Genetic Voyage (Ours) | 5 Matches | ✅ Yes (Visual Overlaps) | ✅ Yes (Local Browser) | ✅ Yes (Local Storage) |
Frequently Asked Questions
❓Why doesn’t AncestryDNA offer a chromosome browser?
AncestryDNA claims that withholding segment data protects customer privacy and prevents law enforcement or third parties from reconstructing users’ genetic profiles. However, this means serious genealogists must download their raw data and upload it to MyHeritage or GEDmatch to perform segment-level analysis.
❓What is the difference between a “fully identical” and “half identical” segment?
A half-identical segment (HIR) means you share DNA with a match on only one chromosome of the pair (either paternal or maternal). This is the standard for most cousin matches. A fully identical segment (FIR) means you share identical DNA on both the maternal and paternal chromosomes at the same position. FIRs are typical in full siblings, double cousins, or heavily endogamous populations.
❓Can a chromosome browser tell if a match is on my maternal or paternal side?
Not directly. A standard chromosome browser only shows that you match on a specific chromosome. To determine if it is maternal or paternal, you must use shared matches: if the match also matches a known cousin from your mother’s side on the same segment, the segment is maternal. Alternatively, testing your parents makes phasing automatic.