Multiple Listing Service (MLS) Details
Updated: Nov 8
The Multiple Listing Service (MLS) is the main way that agents input real estate properties onto the market for sale, and in many cases, for rent. There are different MLS around the country. Some states have only 1, while states like VA have more than 1. Sometimes multiple MLS will intersect to a high degree, with no 1 MLS having more than 50% of the properties in a given city/county (i.e. Williamsburg/James City County), while in other cities/counties, 1 MLS will cover >99.5% of the listings (i.e. Norfolk). Realtors and real estate firms need to pay for access to each MLS. Even when an agent has access to more than 1 MLS, they won't always put their listings in each MLS that they have access to due to the time-consuming nature of MLS entry and paperwork. From the MLS, especially when accompanied by paid programs that companies like Garrett Realty Partners use, the listing auto-populates to 100's of websites where buyers can search for listings.
Here is an MLS map of the US:

Image courtesy National Association of Realtors
MLS in SE Virginia
Here is a close-up of the MLS in Virginia:

Image courtesy National Association of Realtors
Among those MLS, here are the 5 ones that I have access to:

Image courtesy National Association of Realtors
While it's unusual for a real estate agent to have access to 5 MLS, I find it very helpful since I cover a large territory , since I am close in proximity to so many MLS, & want to provide the best services that I can to the buyers and sellers I represent. If I only helped buyers and sellers within the confines of Washington DC, on the other hand, I might only have 1 MLS (BRIGHT), since it's so distant from other MLS on all sides (>80 miles).
Within SE VA, excluding the Eastern Shore, here is a breakdown of the most dominant MLS by city/county according to my research:
Real Estate Information Network (REIN) MLS based out of Virginia Beach:
As you can see above, even in Williamsburg, Williamsburg MLS (WBG MLS Matrix) isn't dominant even in Williamsburg/James City County, although it has a significant presence where it's important to have access there.
(still working on this next one as of 11/29/22)
Central Virginia Regional (CVR) MLS based out of Richmond & Chesapeake Bay & Rivers Association of REALTORS® (CBRAR) MLS:
I group CVR & CBRAR together because, unlike other MLS in SE VA, they have a co-op. The co-op means that any agent with access to 1 can pay an additional amount per year which allows for a single listing data input form to be used instead of 2 (saving tremendous time) & allows for a single search for buyers to cover both MLS.
Northern Neck Association of Realtors/MLS (N Neck):
(still working on this next one as of 11/29/22)
How to Find Out Which MLS are Used Most Outside of SE VA
If you're in SE VA, I've already done the homework for you, but if not, I wanted to share how to find out for yourself.
Whether you're an agent or a buyer, it's best to check on Zillow for which MLS tends to be used from active listings (not sales, since only 1 MLS is placed on Zillow for sales even if the listing was posted on more than 1 MLS). Sometimes that's easier than other times. For instance, in this screenshot of Emporia sales, you notice that only 1 of the properties lists which MLS is being used without you clicking on that property.
In some cases, these are displayed prominently, as in these cases where you see a picture of the MLS logo on the bottom right of each picture of the desktop view on Zillow:

Image courtesy Zillow.com
In many cases in SE VA, they aren't displayed so prominently:

Image courtesy Zillow.com
Those can also be present in some cases on the list view from the mobile app:

Image courtesy Zillow.com
You can toggle between list view and map view on the top left:

Image courtesy Zillow.com
Once you've selected a property, you can scroll down in the information until you see the MLS providing the feed to Zillow. Here's that view from the app:

Here's that view once scrolled down on a property from the desktop version in the overview section:

Just like you can't tell if a property is secondarily listed via the co-op (CVR & CBRAR MLS) on an MLS search, you can't tell on Zillow either.
If you're an agent, the method I used where you check MLS for sold listings, is a solid one for those MLS to quickly acquire a high volume data set that will be very accurate at least for those MLS that you have access to. That said, it's best for agents with more than 1 MLS, with the higher the number of MLS you have making the numbers more and more accurate. For instance, my Williamsburg & James City County #s are likely the most accurate because they have other MLS in between them and MLS that I don't have access to on all sides. On the other hand, you'll notice that on my spreadsheet there are some counties where I had painstakingly go through Zillow on a number of listings to get relatively accurate percentages.
Keep in mind that a single city/county could have 1 MLS having the majority of properties in one section and another MLS having the majority of properties in another section, especially when adjacent to state borders & a large county.
Why Important for Sellers
The higher the exposure of a property in marketing, the more action a home will tend to get with showings, the higher the number of offers, and the higher a home will sell for statistically. Did you know that 29% of buyers found the home they purchased through their agent (NAR)? Because of that, which MLS your home is going to be listed on is a critical question for sellers looking to list the property.
Prior to selling, it's critical to know the MLS makeup of the city/county that you're selling in, and ideal to have MLS exposure on at least 99% of the total listings in that city/county. Some sellers list their property in an MLS that has <10% representation in their city/county without having any idea just how much their agent is hurting them in the process. While I would never do that as an agent, some agents don't mind, especially for sale by owner MLS placement-only agents.
That's especially true in areas of high crossover where a single MLS isn't dominant. In my research, neither Gloucester County nor James City County/Williamsburg had more than 51% of listing sales in a single MLS. When I interviewed a former agent and won the listing, one of the top reasons why he stated he chose me was due to me being in more than 1 MLS. The higher end of the home, the more MLS it will tend to be on as part of a superior marketing package more common to experienced agents than to new agents since most new agents only start with 1 MLS & many agents remain with only 1 throughout their career.
Example:
I've seen where a buyer's agent based out of Richmond reached out to me for a buyer he was representing looking in Hampton where it was obvious that the agent had no idea about the competition in the neighborhood because he was looking on Richmond MLS, which I was advertising in, but where other agents weren't due to the distance from Richmond (about a 1 hr drive) & the low percentage of properties in Hampton that were listed on Richmond MLS (<2.5% last I checked).
Why Important for Buyers
Many buyers are unaware of how much better a search feed on MLS can be vs. a search on public websites common to buyers like Zillow. How much better depends on the MLS, with larger MLS typically having better search features. Unsurprisingly, the least user-friendly MLS I have access to is also the one with the lowest number of members. By establishing a feed with a buyer's agent, you can weed out many of the properties that you wouldn't be able to on public websites, saving you tremendous time and hassle from not needing to look through a number of properties that you wouldn't want. A small number of buyer's agents, myself included, have spent hours on search templates that they can reproduce with a few clicks to start as a baseline for the modifications on your search.
Here's an example of a search baseline I created for USDA buyers where I recreated the USDA map:

Image courtesy Rein.com
I do recommend using both MLS & a search on public websites like Zillow in certain cases (for instance, if you are working with an agent who doesn't have access to the MLS for >99% of the listings in an area or if your search covers a wide territory with many MLS) & in cases with a very high volume of MLS you may be better off skipping MLS searches entirely & setting up a feed just on crossover MLS public sites like Zillow.
One of the most important factors relating to the need to get a buyer search feed going from your agent in Hampton Roads is that most if not all public websites are unable to filter out active contingent listings (under contract with a contingency with a buyer like a home inspection) in a search on REIN MLS. Because of that, many of the properties that appear to be available actually aren't, with no indication of it on public websites except Rein.com (how to check) but even on Rein.com while you can check for contingencies, you can't filter it out of your search like you can with an agent setting up a search for you. I've seen some searches before where there were more active contingent properties than active non-contingent listings.
Did you know that in some cases, a virtual tour is present on listings but not visible on whatever public website you're looking at it (i.e. Zillow)? In some cases, the virtual tour, if present, won't auto-feed to sites like Zillow. If the agent doesn't check behind themselves, it won't be visible, and it's unlikely that agents will check 100's of websites exclusively for that task every time. If you don't see the virtual tour and you're only checking public websites, you may be completely missing what's present that could help you know whether or not you want to see a property. When your time constraints are limited for showings, or when you're driving from a great distance, being able to potentially weed out a property before seeing it through a virtual tour can be very helpful.
Certain MLS have certain features that are superior to anything available on public websites that I've seen. For instance, Matrix MLS, the MLS type used for Williamsburg MLS, CVR, CBRAR, & REIN, has a fantastic flood zone feature, which is very important to SE VA. I haven't seen anything on any public website that comes close unless going to a 3rd party website that isn't integrated into a home search for buyers. I don't even see mention of flood zones on Zillow or Trulia unless the listing agent states something about it in the remarks. I've seen some attempts at looking at flood zones on public websites (i.e. Realtor.com in the Environmental Risk section), but they're not nearly as good as the one integrated into the variants of Matrix MLS. If you only rely on an honest answer to the question, "does the seller pay flood insurance", you can get a wrong or misleading answer from an ignorant listing agent, since some listing agents with access to MLS don't even know how to check for flood zones, & if they know how to, they may not care to. Did you know that they may respond by honestly saying that they don't pay flood insurance, but might not disclose that you would need to if you are buying the same house with a mortgage? That's right; those who don't have a mortgage on a home aren't required to pay flood insurance.
Here's an example of a public website's attempt at showing flood zone information:

Image courtesy Realtor.com
On Matrix, the portal I use for most MLS in the area (excluding Northern Neck), I can see a map of the flood zone which can give me a much better idea about if the property will require flood insurance for a mortgage & give me a better idea about the likelihood of the property flooding because I can look at the surrounding area's flood zones as well.
In addition to virtual tours, contingencies, & features, there are a number of other elements that you won't see on most public websites that will be visible on MLS. You may see things like bedroom dimensions, the square footage of the garage, room types, whether or not the property is eligible for a loan if you're using one with specifications about which loan types would be possible, etc.
I've seen where it took a few days delay for a property to be listed on Zillow from the day that it hit the market on MLS. In some cases, a property can be under contract at that point. I don't believe that this issue is nearly as bad as it was years ago though.
Agent remarks in listings sometimes provide critical information that your buyer's agent will be going blind without. For instance, there could be an offer deadline in 12 hrs listed in the agent remarks, and your agent may be unable to reach a deadbeat listing agent if they happen to be one during those 12 hrs. There could be showing instructions listed in those agent remarks that likewise wouldn't be visible to your agent unless they gain access to those agent remarks.
Another reason why it's good for your agent to have access to the MLS of the cities/counties where you're looking is because of lockbox access. While it's not always the case (i.e. Northern Neck MLS), many MLS have proprietary lockboxes that can only be used by members of that MLS. If you don't have access to that proprietary MLS, in some cases, you may not be able to get in before a property goes under contract if your agent doesn't have direct access to the lockboxes that he or she can only access by them and their company paying monthly/annual dues to that MLS. Even if your agent is willing to pay up and learn a new system, their company may not be if they aren't already paying.
Another reason why it's good for your agent to have access to the MLS of the cities/counties where you're looking is due to the chances of offer success & mitigating issues. Agent experience is a positive element of a buyer's agent looking to make an offer from a seller's & listing agent's perspective in many cases (though not always, as you'll see below), but if you are working with an agent where they are asking for the offer form because they don't have access to it, that looks bad for you as a buyer if the property ends up being in a competing offer scenario. If it takes the listing agent too long to provide it, the property could be under contract by the time it's filled out. Using an offer form the listing agent is unfamiliar with is going to weaken the offer's chances of success. Also, if your buyer's agent is completely unfamiliar with an offer type that the listing agent likes and your agent is using it for the first time, they are more likely to make mistakes that could cost you as the buyer money or could cost you the whole transaction if you aren't careful. For instance, I once represented a seller where the buyer's agent wasn't familiar with the VAR offer she was using. While it's not the primary offer I use (REIN offers are), I've taken a greater than 6-hour course on it and am more familiar with it than most in my area. The buyer banked on the seller taking care of moisture problems that they believed were present in an area, telling me so shortly after contract ratification. I replied that the moisture inspection she was referring to wasn't in their offer, since it's in a REIN offer as a requirement by the seller to pay for up to 1% (by default, though that number can vary based on the offer) of the purchase price in issues, but not a VAR offer. If the moisture problems that they alleged had been legitimate, sometimes those can be pricey to remedy.
Some sellers list their property in an MLS that has <10% representation in their city/county without having any idea just how much their agent is hurting them in the process. While I would never do that as an agent, some agents don't mind, especially for sale by owner MLS placement-only agents. That said, buyers agents with access to more MLS have a higher probability of having the MLS of the listing in these scenarios. For instance, I've seen where a listing agent listed a property in a location with <10% MLS exposure of an area (Williamsburg), with an 888 # under the listing agent's # since it was an MLS placement-only listing & the listing agent remarks, visible only to those with MLS access, stated, "This is an MLS Placement Limited Service Listing. Please deal with (the owner's name) directly at #### with
showings, inquiries, offers and everything else till closing. Email listing agent once contract is ratified so status can be updated." Without access to the MLS for that listing, or assistance from another buyer's agent who had it, the buyer wouldn't be able to access the property readily. Since expeditious showings are so important, MLS access can be key to getting into a house, writing an offer, and getting under contract before your competition.
Areas of Crossover MLS
There are some areas in SE VA & otherwise with high crossover where a single MLS isn't dominant. For instance, out of 669 MLS listing sales I analyzed in Gloucester County, 50.22% were from REIN MLS, 40.81% were part of CBRAR &/or CVR MLS, & 7.62% were part of Williamsburg MLS. Gloucester isn't alone. In Williamsburg/James City County, out of 2522 listing sales, 44.81% were in REIN MLS, 42.43% were in Williamsburg MLS, & 12.21% were in CVR &/or CBRAR MLS. Conversely, a city like Norfolk had >99% dominance to a single MLS among local MLS (not counting for sale by owner listings).
Commercial MLS
In addition to residential MLS, there are also commercial MLS, which I get into here.
How Working with an Agent w/ Access to a Higher # of MLS Can Help
If an Agent Doesn't Have MLS Access, What Can They Do?
Buyers Agents:
Agents who frequently don't have MLS access to properties for buyers should consider referring their buyers to another agent, especially if they don't have easy access to lockboxes in some way. For instance, if you don't have access to REIN lockboxes in Hampton Roads, most listings won't be accessible to you unless you meet someone there because most listing agents don't abide by the best practice of always having a contractor lockbox on a property as a backup. On REIN lockboxes, there is no coded entry.
Agents who infrequently don't have MLS access to properties for a buyer can sometimes get additional information from their NARRPR account's view of a listing, such as whether or not a lockbox is on the property in some cases. That information will typically not be on public websites, but being a Realtor provides access to a NARRPR account. That said, NARRPR information still may not provide you with the information that you'll need. In that case, you may need to contact the listing agent, and in some cases, when the number to the listing agent doesn't actually get to a listing agent, it's best to reach out to another agent that you know has access to that MLS for information. Advanced notice is ideal in this scenario, slowing down showings in a negative fashion for buyers at times, with expeditious showings being critical for the buyers you work with.
Listing Agents:
Listing agents who can't provide good MLS coverage for a listing by % of coverage shouldn't take the listing. I you don't have access to >80% for low-end properties and >95% for high-end properties of MLS-based listings in a location, reconsider listing there, recalling your fiduciary duties to take your clients' interests above your own at all times. Consider referring them to another agent.
Related:
Which Multiple Listing Service(s) Are Needed to List in SE VA?
Most Important Cities/Counties in Hampton Roads for Multiple MLS