Just google once and you will get lots of website for website or webpage audit for free. https://www.google.co.in/search?client=opera&q=free+website+audit+tools&sourceid=opera&ie=UTF-8&oe=UTF-8
I don't think there are a good FREE website audit service out there. If just about Onpage Optimization factor, then may be yes. Since it's only crawl one page. Woorank or Sitechecker can do it. But if you include technical SEO audit then it's will consume a lot of resources since it need to crawl your entire site, too much for a FREE tool.
Yes if it's a technical SEO audit then it'll be tricky to find a completely free one. However there is CocoScan (https://cocoscan.io) which gives you 1000 free pages to scan- this may help you.
If you google 'Free SEO webpage audit', you will see lots of tools. They are actually pretty similar and offer some basic information about your page. As it was mentioned earlier, you can try woorank, seoptimer, neilpatel's tool etc. etc. If you need to conduct in-depth website analysis, I'd recommend using some advanced paid tools such as Ahrefs, Serpstat or SEO crawlers like Netpeak Spider.