Though eBay doesn't dominate the online marketplace in quite the way it once did, thanks to endless competitors vying for attention, it's still an excellent place to sell your new and used items. If you're considering listing something on eBay, there's a major question to answer: do you use the auction or Buy It Now format?

On eBay, Buy It Now is the name for a fixed price listing that runs indefinitely until sold. On the other hand, there's an auction, which runs for a specified number of days and lets buyers bid increasing amounts to win the item.

But which of these eBay selling strategies is the best? As you might imagine, the answer to that question isn't simple, and it depends on a range of factors like the rarity of your item, how quickly you want to sell it, and how many people you wish to see your listing.

Without further ado, these are the questions to ask yourself to decide between an auction and Buy It Now.

1. How Many People Want Your Item?

Do your best to establish what the demand is for your item. You might possess something valuable, but how many people actually want to buy it? If the buying pool is slim, those people might not see your listing immediately—or ever, if they don't use eBay.

Auctions run for 10 days maximum. If only a couple of people see your listing in that time, the item is unlikely to sell for its highest price because there will be less of a bidding frenzy, no matter how rare your item is. You may find it more profitable to set your desired Buy It Now price and let the listing run longer.

On the other hand, if the demand is high and the supply is low, opt for an auction. You can let the market determine the price, which might be far greater than you expect. Because people will be so keen to get their hands on your item, a bidding war can ensue and bidders will keep one-upping each other right until the last second. You could end up making lots of money on eBay.

2. How Quickly Do You Want to Sell?

If you're more interested in shifting the product quickly and less concerned about how much money you make from it, consider an auction. You can run an auction for as little as one day if you have a feedback score of at least 10 (otherwise it's three days).

While you could list your item as Buy It Now and see it snapped up in under 24 hours, a soon-to-end auction will put the fire into a buyer. Of course, the fewer days you list your item for, the fewer people will be exposed to it. You might end up selling your item for 99 cents through a one-day auction, so be aware of that risk.

Regardless of whether you opt for an auction or Buy It Now, the buyer must pay within four days of the listing finishing.

3. How Many Units Are You Selling?

If you have multiple copies of the same item, consider selling at a fixed price. This is because you can take advantage of eBay's bulk selling features. You select the price, enter your quantity, and the listing runs until you're out of stock.

You only need to manage a single listing via this method, no matter your quantity. This means you can quickly change the product details and price within a few steps, rather than fumbling through multiple listings.

The downside is that you're not going to sell all your stock at the same time, and you'll have to send it out in batches. If you want to avoid this, multiple auction listings set to expire at the same time might be preferable.

4. Do You Want to Solicit Offers?

eBay has a feature called Best Offer, which you can enable on both auction and Buy It Now listings. With Best Offer, it allows potential buyers to offer a price that they're willing to pay for an immediate purchase. You can accept, reject, or counter this offer.

On a Buy It Now listing, the Best Offer feature remains available until someone buys the product (aka, the listing ends). On an auction, it's only available until someone makes the first bid. As such, you have a greater chance of receiving offers through a fixed price listing than you do an auction, unless your auction remains without bids for a long period.

As a seller, the benefit to soliciting offers is that you can sell the item quickly, and potentially at a higher price than it would sell through auction. Just be wary of eBay scammers who message you an offer and they want to finalize outside of eBay—you'll have no protection if the transaction goes wrong.

5. What Are Other Sellers Doing?

If you can't decide what type of listing to choose, check out what other sellers are doing currently and have done in the past. To do this, search for your item and, on the left-hand filters, look beneath Buying format. This will show you how many are auction versus Buy It Now, along with how many accept offers.

To see historical performance, look for the Show only filter category and select Sold items. At the top, you can filter by Highest price. This will give you a good indication of which format generally secured the largest returns. Researching past sales is a great way to sell more on eBay.

You'll typically find that Buy It Now listings heavily outnumber auctions nowadays, in part because so many small businesses and larger retailers use eBay as one of many branches to sell their products. But don't let this skew your judgement—if you think an auction is going to lead to greater success, go for it.

Should You Choose an eBay Auction or Buy It Now?

If your item is in high demand, low supply, and you want to make the most money, opt for an auction. If you time it right, and with a bit of luck, you'll witness a bidding war. Alternatively, if you have no urgency to sell, want to list in bulk, or want a greater chance of receiving offers, go for a fixed price Buy It Now listing.

Whatever you decide to do, take original photos, clearly describe your item, and correctly calculate the shipping. If you don't, you're making some of the biggest eBay mistakes.