Before purchasing an SSL certificate, make sure to understand these things. It can save you a lot of unnecessary expenses.

Today, let's talk about the pitfalls that must be understood before purchasing an SSL certificate. Let's start with the most crucial question: What level of certificate do you actually need? SSL certificates are divided into three categories: DV, OV, and EV. The difference lies not in the encryption strength (they are the same in terms of encryption technology), but in the extent to which "who you are" is verified. DV is the most basic, only verifying whether you have control over the domain name. It can be issued in just ten minutes and is relatively inexpensive. It's sufficient for personal blogs and testing sites. However, it has a drawback: it does not verify the identity of the enterprise. This means that hackers can register a domain name that looks similar to "taoba0.com" and obtain a DV certificate. The browser will still display the little lock - users won't be able to tell the difference between the genuine and the fake.

The OV certificate has taken another step forward. The CA institution will actually check your company's business license and verify the company's existence status. The details of the certificate will display your company's name. For small and medium-sized enterprises with websites or on e-commerce platforms, if you want to make users feel more at ease, this level is more suitable. EV is the highest level and has the strictest review process. Previously, the company name would be displayed in green directly in the browser address bar. Although the UI has been changed, it is still the preferred choice for high-sensitive scenarios such as finance and government affairs.

So the first thing to figure out is: Do you merely want to ensure that data is encrypted during transmission, or do you also want to let users know that "this company actually exists"? The former requires DV (Data Verification), while the latter requires OV (Online Verification).

The second point that is prone to causing mistakes is the type of domain name.

Many people think that "I buy a certificate and all subdomains of the website will be protected" - that's not the case. A single domain certificate can only protect the domain name you enter, such as www.example.com. demo.example.com is not within the protection scope. Wildcard certificates can protect all subdomains at the same level like *.example.com. If you have multiple completely different domain names, such as a.com and b.com, then you need to purchase a multi-domain certificate or buy two separate certificates.

There is another situation that is often overlooked: If your service is accessed directly via a public IP (such as some internal systems or IoT devices), regular certificates do not support binding to an IP. Only OV single-domain certificates from brands like GlobalSign, DigiCert, and GeoTrust are available. My friend fell into this pitfall and suffered a lot.

The third change that needs to be noted this year is that the validity period of the certificates has shortened.

Starting from March 2026, the maximum validity period for all newly issued public trust SSL certificates has been shortened to 200 days. The days when you could purchase a certificate for one year have passed. Now, you pay for a one-year period but receive a "subscription service" - the first certificate has a validity period of 199 days, and before it expires, you need to manually "renew" to obtain the second one in order to reach a total of 365 days. If you forget to act within the 30-day window, the latter part becomes invalid and you have to buy a new one.

This poses a challenge for the operation and maintenance team. Previously, they only needed to worry about it once a year, but now they have to deal with it every six months. Some service providers offer automated renewal reminders and even automatic deployment. When making a purchase, you can take this factor into consideration.

The fourth question is about algorithms and compatibility.

Currently, the mainstream algorithms are RSA and ECC. RSA has the best compatibility, and it can be recognized by old devices and browsers. The minimum requirement is 2048-bit, and 4096-bit is even more secure. The ECC algorithm is more advanced. Under the same security level, it has shorter keys, faster encryption and decryption speeds, and lower resource consumption. It is more friendly to mobile devices and IoT devices. If your user group mainly consists of domestic users and the device environment is relatively new, ECC provides a better experience; if you are targeting the global market and there are still a large number of old devices accessing, RSA is more reliable.

Another option is the national encryption SM2 algorithm. This algorithm is applicable in scenarios with compliance requirements such as government affairs and finance. Ordinary websites do not need to worry about it for now.

The fifth point that is often overlooked is the selection of the service provider.

SSL certificates are not something that can be simply purchased and installed. What if there are errors during the configuration process? What if the certificate expires and you forget to renew it? How do you apply for multiple domain certificates in a combined manner? Do you have technical support and how responsive is it? This directly affects whether it's convenient to use in the future. Well-known brands such as DigiCert, GlobalSign, and CFCA have root certificates that are trusted by all browsers and operating systems, and there won't be any awkward situations like "untrusted". Some small service providers may be cheaper, but their root certificates may not be widely available, or their technical support may not keep up. The money saved ends up being wasted on time-consuming efforts.

Finally, let's talk about the free certificates.

Free SSL certificates may save you money, but don't put them in your production environment, let alone in sites that handle transactions or involve privacy. Besides the identity verification vulnerability mentioned earlier, free certificates often expire without being managed because of renewal difficulties, and the website suddenly becomes inaccessible. Saving those few hundred dollars comes at the cost of user complaints and loss of trust. It's not worth it.

In summary, before purchasing an SSL certificate, ask yourself the following questions: Are you an individual or an enterprise? Do you only need to encrypt data or do you also need to showcase your identity? How many domains need protection? What devices do users use to access? Is there anyone to help with the maintenance? Once you have clear answers to these questions, then you can look at the brand, select the type, and compare the prices. Only then will you have a clear understanding.