What are some alternatives?
When comparing SEO Tool Extension and SEO Toolbox by OnCrawl, you can also consider the following products
SEOtooList - Find the best SEO tool for the right job (community curated)
MaaxMarket SEO Audit - A simple, beautiful SEO audit tool that tells all you need
SEO Minion - Chrome extension & Firefox add-on to help you with SEO
SEOmator - SEO website analysis & audit tool
SEO Prompts - SEO without the headache
Magento SEO Extension - Complete on-page SEO solution for Magento