The popularity of online shopping was already on the rise before 2020, and the pandemic only accelerated its growth. eCommerce’s share of global retail trade went from 14% in 2019 to about 17% in 2020, according to the UN. As a result, new eCommerce stores are popping up every day, and traditionally brick-and-mortar brands are now focusing on their online shopping interfaces more than ever.

In 2021, the easiest way for small- and medium-sized businesses to establish an online store is by using a SaaS service for eCommerce. Third-party platforms can significantly reduce the time and cost of developing and operating an eCommerce store. Today, Shopify, WooCommerce, and BigCommerce are three of the most popular eCommerce platforms on the market. Whichever service you choose to use, there are plenty of third-party apps and plugins you can integrate to make your store even more effective. Here are five of the most useful, which we recommend for online merchants on any of these three popular platforms.

#1. Sendinblue

 Selling on Shopify, WooCommerce, or BigCommerce? You Should Be Using These 5 Apps

Sendinblue is an automation tool that makes designing, delivering, and tracking digital communications like emails and SMS messages much easier for eCommerce business owners. Since customer communication is an essential part of any online store’s success, this tool is a must-have for merchants on all platforms.

Key Features

  • Multiple ways to reach your customers with personalized messages, including email, SMS, and chat
  • Customized transactional emails, landing pages, and sign-up forms to inspire brand trust with professionalism and consistency
  • Real-time statistics, A/B testing, and data reports to help you optimize your marketing campaigns

Pricing

Sendinblue offers a free trial and a free plan, with which you can send up to 300 emails. Paid plans start at $25 USD per month and include extra features like A/B testing and branded templates. Comparing the same features and limitations, Sendinblue has a great price advantage over Mailchimp, another well-known email marketing platform.

#2. Kiwi Sizing

 Selling on Shopify, WooCommerce, or BigCommerce? You Should Be Using These 5 Apps

Poor fit (often due to an incorrect sizing choice) is the most common reason for customers to return an online order. If you want to reduce returns, then, having an informative sizing tool on-site is crucial. Kiwi Sizing is an app that makes creating helpful sizing charts easy. It was first launched on Shopify, and after receiving many excellent reviews there, it was soon integrated with other major eCommerce platforms as well. (Recently, the Kiwi Sizing integration with Wix was also launched.)

Key Features

  • Three types of size recommenders and fit recommnders that use an AI-based engine to provide accurate sizing recommendations after customers enter basic details about their body type or measurements
  • Customized sizing charts for all sorts of unique products from apparel to sports gear, complete with built-in, automatic unit conversions to help customers from different parts of the world find the correct size
  • A powerful analytics dashboard that lets you know how customers are using your tools, so you can optimize your sizing charts accordingly to boost sales

Pricing

Kiwi Sizing offers a free version of their tool, which comes with two fully customizable size charts and an automatic unit converter. Premium plans provide more advanced size recommenders plus detailed analytics. Their plans start at $7.49 USD per month and increase on a sliding scale according to the number of views. Free trials are available for upgraded plans.

#3. Affirm

 Selling on Shopify, WooCommerce, or BigCommerce? You Should Be Using These 5 Apps

Third-party payment gateways are usually preferred to protect the rights and interests of eCommerce sellers, so they can ship the goods only after clearing the payment. But recently, the buy-now-pay-later type of payment service has become increasingly popular because of how sharply it can increase conversions. Affirm is one app that allows shoppers to buy an item immediately and pay for it later, up to $17,500. This option is especially useful for sellers offering high-priced items who want to increase sales.

Key Features

  • Lets customers buy almost anything from any merchant that accepts Visa, and pay for it later
  • A credit limit up to $17,500, which is the highest in the market so far
  • Easy integration with different eCommerce platforms

Pricing

Affirm doesn’t show pricing on their official website, and requires that you contact them directly before installing the app for your eCommerce shop. There are some criteria to meet before you’ll be approved to offer Affirm, like having a bank account in the US and listing prices in USD.

#4. OptinMonster

 Selling on Shopify, WooCommerce, or BigCommerce? You Should Be Using These 5 Apps

A good conversion strategy is critical for any eCommerce business. Without one, it’s impossible to meaningfully grow your email list and bring in more sales that way. OptinMonster is a popular tool to help with this, assisting sellers in driving engagement and sales and even in recovering abandoned carts.

Key Features

  • A drag-and-drop editor that lets you create marketing campaigns that will grab the attention of your site visitors and help convert them into customers
  • Pop-ups that can be triggered by exit intent, so you can entice shoppers to spend more time on your site
  • Easy creation of targeted opt-in campaigns that let you tailor messages for returning visitors so you can turn them into repeat customers

Pricing

OptinMonster’s basic plan starts at as low as $9 USD per month, which includes unlimited campaigns, list segmentation, and 2,500 pageviews on one site. Its more advanced plans offer more in-depth features, and cost up to $49 USD per month. OptinMonster doesn’t provide a free trial, but they do guarantee a 14-day unconditional refund if your needs aren’t satisfied.  

#5. JivoChat

 Selling on Shopify, WooCommerce, or BigCommerce? You Should Be Using These 5 Apps

In addition to great products and smart marketing strategies, excellent customer support is a must-have if you want to create long-term success for your brand. JivoChat is an app that makes it easy for customers to contact you when they’re looking for information about sizing, product details, return policies, discounts, etc. It gives you the opportunity to improve conversion rates and build brand loyalty by providing a great customer experience of fast and high-quality service across channels.

Key Features

  • A contact point for customers on all major channels, including your website, WhatsApp, Instagram, Facebook, and more
  • An automated chatbot to help you reduce the workload of your human customer-service agents
  • A built-in CRM system that can be customized to manage all deals and sales for your business

Pricing

JivoChat has a simple pricing model: The Basic plan is always free, and the Professional plan adds up to $19 USD per agent per month (if billed annually).

The right suite of apps is your recipe for success

There are lots of third-party apps out there that can be integrated with Shopify, WooCommerce, and BigCommerce. The five we’ve covered here are popular, highly rated options that have already helped scores of online merchants build their digital businesses. Sign up for a few today to help your eCommerce business get started or grow!


Kiwi Sizing is an e-commerce plugin to help solve the sizing problems for online shopping. Over 40% of online clothing returns are due to sizes. Kiwi Sizing is designed to make sizing easy by offering stylish size charts and easy-to-use fit recommenders that let shoppers know what is the best size to purchase. We help improve conversions, cut down on returns, and lower the needs for customer support.

We are trusted by thousands of Shopify stores with over 400 5-star reviews. Try it now for free and start reducing unnecessary returns.