The best small business credit cards to use for Facebook, Google and other online advertising

Anyone with a small business or side hustle should have a small business credit card that earns bonus rewards in areas where they spend the most.

A major expense for many businesses is digital advertising, including platforms like Facebook, Google, Amazon and Twitter. If you're not maximizing the rewards you earn for your business's online advertising, you may be missing out on a major opportunity.

Below, CNBC Select has compiled a list of the best business credit cards for online advertising, including cards that earn travel rewards, airline miles and cash back. (See our methodology for more information on how we choose the best cards.)

The American Express® Business Gold Card stands out for its flexibility. Cardholders earn an impressive 4X Membership Rewards® points on the 2 categories where your business spends the most each billing cycle from 6 eligible categories. While your top 2 categories may change, you will earn 4X points on the first $150,000 in combined purchases from these categories each calendar year (then 1X thereafter). Only the top 2 categories each billing cycle will count towards the $150,000 cap. Terms apply.

The American Express Business Gold's bonus categories include U.S. purchases for advertising in select media and lots of other useful categories such as U.S. purchases at gas stations, restaurants, for shipping and more.

To qualify for the bonus rewards, American Express purchases must be made directly from U.S. media providers (online, TV, radio). This includes (but is not limited to) advertising purchases with companies such as Google, Facebook, Yahoo and CBS.

In addition to transferring American Express Membership Rewards® points to various airline and hotel partners, cardholders can redeem their points toward eligible airfare booked through the Amex Travel Portal and receive a 25% points rebate (up to 250,000 points per calendar year). The rebate applies to business and first class tickets on any airline, or any class on your selected qualifying airline.

The Ink Business Preferred® Credit Card offers a reasonable $95 annual fee, a sizeable welcome bonus and generous returns. It earns 3X Chase Ultimate Rewards® points in useful categories for business owners, including travel, shipping purchases, Internet, cable and phone services and advertising purchases made with social media sites and search engines — for the first $150,000 in combined purchases each account anniversary — as well as 1X points for all other purchases.

Chase Ultimate Rewards® points are excellent travel rewards because they give you many options. You can redeem points for one cent each as cash back or book travel through Chase Travel^SM at a rate of 1.25 cents per point. You can also transfer Chase points to 14 travel partners to book flights or hotels.

Other benefits include no foreign transaction fees, primary car rental insurance, cell phone protection, employee cards at no additional cost and more.

The Blue Business® Plus Credit Card from American Express is an excellent no-annual-fee business credit card (see rates and fees). What makes this card so special is that you earn 2X American Express Membership Rewards^® points on the first $50,000 in spending per calendar year, then 1X points — there are no bonus categories to keep track of. Terms apply.

The Blue Business Plus card's simplicity makes it a great card for anyone starting a side hustle or small business. Plus, you can invest in your business by financing new purchases with a 0% intro APR on purchases for 12 months from the date of account opening, then (18.49% - 26.49% variable APR thereafter, see rates and fees). However, as your business grows, you may want to look at other cards once your credit card expenses exceed $50,000 a year.

The *Capital One Spark Cash Plus Credit Card removes the headaches of earning and redeeming credit card rewards. It earns an unlimited 2% cash back on every purchase, and it's a charge card with no preset spending limit, so you'll need to pay it off in full each month.

The *Capital One Spark Cash Plus is ideal for anyone looking for a set-it-and-forget-it card because there are no complicated benefits or rewards to navigate. It does have a $150 annual fee, but you can get it refunded after spending at least $150,000 on the card in a year. It's also free to add employee cards that earn 2 and there are no foreign transaction fees.

The Southwest® Rapid Rewards® Performance Business Credit Card is great for business owners who prefer to earn rewards with an airline. This card earns 2X Rapid Rewards points on social media and search engine advertising.

Southwest has a simple loyalty program that allows you to book any seat with points because the price of an award ticket is tied to the cash price. This is helpful for business travelers whose schedules may be less flexible. Plus the card has a host of other benefits, including a Global Entry or TSA PreCheck application fee credit (worth up to $100), 365 inflight Wi-Fi credits per year, four upgraded boardings per year (when available), and more. Plus, the Southwest points you earn with this card count toward earning the Southwest Companion Pass.

Online advertising is a common expense for many businesses, and with the right business card, you can maximize the rewards you earn for this type of purchase. You can also choose a card that earns the type of rewards that will be most useful to you, whether that's straight cash back, airline miles or travel rewards. Plus, many of the cards on this list earn bonus rewards for a variety of other purchases as well, so your business can be rewarded for more than just its spending on ads.

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At CNBC Select, our mission is to provide our readers with high-quality service journalism and comprehensive consumer advice so they can make informed decisions with their money. Every credit card list is based on rigorous reporting by our team of expert writers and editors with extensive knowledge of credit card products. While CNBC Select earns a commission from affiliate partners on many offers and links, we create all our content without input from our commercial team or any outside third parties, and we pride ourselves on our journalistic standards and ethics. See our methodology for more information on how we choose the best small business credit cards.

To determine which business cards offer the best value for online advertising, CNBC Select analyzed the most popular credit cards available to U.S. business owners. We compared each card on a range of features, including the annual fee, employee card fee, rewards, welcome bonus, introductory and standard APR and foreign transaction fees, as well as factors such as required credit and customer reviews when available. We also considered additional perks, the application process and how easy it is to redeem points.

*Information about the Capital One Spark Cash Plus Credit Card has been collected independently by Select and has not been reviewed or provided by the issuer of the card prior to publication.

For rates and fees of the Business Gold Card® from American Express, click here.

For rates and fees of the Blue Business® Plus Credit Card from American Express, click here.