Summarize:

Click in the address bar of the website and look at the first part of the URL. If the site uses "https" before the rest of the address, then it has transfer layer security (TLS), which helps encrypt your data so hackers or scammers have more difficulty accessing your information. If the website only contains "http", then it doesn't have the TLS certification and won't encrypt your data. Avoid buying or selling on that site so you don't have your information stolen. Most browsers will show a lock symbol in the address bar if you're on a secure site. You can buy and sell safely from sites like Amazon, Facebook Marketplace, Craigslist, eBay, and Etsy. Scroll through the website and read the postings and information listed for the products. Carefully check for common spelling or grammatical errors since they could be a sign the site was put together quickly and may not be trustworthy. Click through multiple pages on the site to determine if there are errors throughout the site, or if it was just an accident on 1 page. If you aren't sure if there are spelling or grammar errors, try copying the text and pasting it into a text document so you can run a spell checker. Pay attention to strange formatting as well, such as sentences written in all caps or with strange symbols, since they could also signify the website is untrustworthy. Spelling and grammar errors are most prominent on Craigslist, Facebook, and eBay, but you may find them on other sites as well. Click on the seller's profile and look for any ratings or reviews that other users have left for them. Read through the reviews so you can learn what past experiences others have had with the seller. If they seem mostly positive, then you can probably trust them. If you see a lot of negative reviews, then you may want to try looking for a different seller. You can also search online for the name of the site where you're shopping followed by the term "reviews" or "scam" to see if other people have posted about their experiences. If you don't see any reviews or ratings, the seller may be new and could potentially be a scam. Be wary of reviews that use the same wording or have reviews posted within a few hours of one another since they could possibly be bots or spam reviews. This works great on sites like eBay, Etsy, Facebook, and Amazon. Scroll to the bottom of the webpage and look for a section labeled "Consumer Protection Policy" or something similar. If you don't see one listed, then it may not offer the same level of protection for any information you enter on the site. You may also check the site for a return policy, and avoid buying items that don't offer refunds or exchanges. Some legitimate websites may not offer refunds or returns depending on the products they sell, such as digital games or movies. If the site doesn't offer returns but you aren't sure if you can trust it, look for other signs that it may be a scam. Check the listed prices for the items you're interested in on the site that you're questioning. Look up the same product on a secure marketplace, such as Amazon, or compare what other people are selling the item for on sites like Craigslist or eBay. If you notice the listed price is discounted by more than 55% than what other sites are selling for, it may be a scam and you should avoid using the site. Trust your gut instinct when you find a new website. If you don't immediately feel good about shopping on it, then avoid using it anymore. Some untrustworthy sites will list sales or deals that only last a few hours to try and get you to purchase something, but these are usually done to attract more visitors. If you're buying a vehicle online, check the value using Kelley Blue Book or another trusted site so you know the actual market value. Right-click on the image on the posting and paste it into a search engine before clicking enter. If you don't get any search results, then the user took the image themselves and hasn't posted it anywhere. Otherwise, scroll through the results to see if the image was posted somewhere else. If you notice the same user or person sharing the image, make sure the information matches between the postings, or else it could be a scam. If you're shopping on Craigslist, eBay, or Facebook Marketplace, avoid buying items that only have stock images as pictures since the person may not actually have the product or the condition may be worse than what's listed.
Use sites that have URLs starting with "https" to ensure they're secure. Watch out for poor grammar and spelling. Check the seller's feedback rating if you're able to. Look for consumer protection or return policies on the page. Be wary of items listed below market value. Do a reverse image search to see if sellers have reused pictures.