23andMe

 
At 23andMe, go to the bottom of your DNA Relatives page and select "Request DNA Relatives Data Download" that is shown below enclosed in a red square and pointed to by the red arrow:
 
 
Despite the help button saying that it may take up to 12 hours to prepare, it likely will take at most a minute or two. You'll know it is completed when the blue request button changes to a black "Download DNA Relatives Data button":
You'll also get an email telling you your file is ready, but if you've waited and it changed, then you don't need the email.
 
Clicking the download button will download a special file named:   nnnnnn_relatives_download.zip
where:
   nnnnnn is your name (with underscores instead of spaces)
   .zip indicates this is a compressed file
 
Then open Windows Explorer in the directory you saved the file, and right-click on it and use the Windows 7-Zip utility to "Extract Here" (or use another unzipping program of your choice).
 
 
You will get a file named:  nnnnnn_relatives_download.zip which has the same file name but a .csv extension.
  .csv indicates this is a comma delimited file which can be read by Excel and other programs.
 
This .csv file is the file you use with DMT.
 
Important note:  23andMe does not include the name of the tester in the file. The nnnnnn in the filename is the only indication of who the tester is. DMT will use the name in the filename replacing underscores with spaces as the name of the tester. If that name is not found in other people's match files, then you won't match. If you find this happening, you will need to change the filename to match how the person is named in other people's match files.
 
Do not rename the "_relatives_download" part of the segment match file names or change their ".csv" extension. DMT looks for that to find segment match files and will not accept files not following that structure.  However, you may change the filename after the word download. I often add the date so that I can compare with my previous download to see what new matches have been added, e.g:
nnnnnn_relatives_download_yyyymmdd.csv
 
When loaded into Excel, the file can be seen to contain all the chromosome segment matches, as well as a lot of other information in columns to the right that DMT does not use:
 
Column A (Display Name) is the full name of the person who matches.
Column B (Surname) is the surname of the person who matches.
Column C (Chromosome Number), D (Chromosome Start Point) and E (Chromosome End Point) is the chromosome number with the start and end locations of the matching segment on that chromosome.
Columns F (Genetic Distance) and G (# SNPs) is the distance in Centimorgans (cM) and number of SNPs for the matching segment.
Columns H through AD contain additional data including: Full IBD, Link to Profile Page, Sex, Birth Year, Set Relationship, Predicted Relationship, Relative Range, Percent DNA Shared, # Segments Shared, Maternal Side, Paternal Side, Maternal Haplogroup, Paternal Haplogroup, Family Surnames, Family Locations, Maternal Grandmother Birth Country, Maternal Grandfather Birth Country, Paternal Grandmother Birth Country, Paternal Grandfather Birth Country, Notes, Sharing Status, Showing Ancestry Results, Family Tree URL. - These fields are not used by DMT.
 
 

Using DNAGedcom

 
You can use the DNAGedcom Client program to download other people's segment match information if they are in your match list.  This is a Windows program available from https://www.dnagedcom.com. They charge $5 a month to use the program.
 
After you download and login to the program, then you go to the Gather page and Select 23andMe. On that page, you then enter your 23andMe login information and press Login. Select your Profile. Then press "Gather Matches". Once you've done that, you'll see in the dropdown under "Choose ICW to Gather" will be a list of all your 23andMe matches. You can select any of them and then press the "Gather ICW" button.
 
Although they are calling this ICW (In Common With), you are actually getting all the individual segment matches with the people you match to, which is exactly what DMT uses.
 
This will download a file named:   nnnnnn_23andMe_FIA.csv, where:
   nnnnnn is your match's name
   .csv indicates this is a comma delimited file which can be read by Excel and other programs.
The file will be put in the folder where your DNAGedcom database is located. (In DNAGedcom, the DB Folder is set in Home->Settings)
 
Do not rename the "23andMe_FIA" part of the segment match file names or change their ".csv" extension. DMT looks for that to find DNAGedcom-produced segment match files for 23andMe and will not accept files not following that structure.  However, you may change the filename after the word FIA.  I often add the date so that I can compare with my previous download to see what new matches have been added, e.g:
nnnnnn_23andMe_FIA_yyyymmdd.csv
 
When loaded into Excel, the file can be seen to contain all the chromosome segment matches, as well as information in columns to the right that DMT does not use:
 
 
Column A (Person 1) is the full name of the DNA Tester.
Column B (Person 2) is the full name of the person who matches.
Column C (Chromosome), D (StartPoint) and E (EndPoint) is the chromosome number with the start and end locations of the matching segment on that chromosome.
Columns F (GeneticDistance) and G (SNPs) is the distance in Centimorgans (cM) and number of SNPs for the matching segment.
Columns H and I are the 23andMe ID numbers of Person 1 and Person 2.
 
Note that this file does include the DNA Tester's name in the first column.
 
DMT accepts both the 23andMe relatives download file and the DNAGedcom 23andMe FIA file as valid 23andMe segment match files.
 
DMT does not accept the DNAGedcom Overlap_23andMe_FIA file from their "Gather Matches that Overlap each other" dropdown option, nor does it accept the Combined_23andMe_FIA file from their "Gather ALL Matches" dropdown option.
 
DNAGedcom selects many of the same set of people for the segment matches that 23andMe selects, but there are some people each include that the other doesn't. You can compare DNAGedcom FIA files with 23andMe relative_download files, but you'll get more people common if you just compare FIA with FIA or 23andMe with 23andMe than if you mix them.