On-Page SEO refers to the optimisation of your actual website, such as Optimised Content, Relevance, Target Keywords, Internal Links, User Experience (UX), Accessibility, URL Structure and Technical SEO.
Is On-Page SEO Important?
Absolutely, yes. According to Google's 'How Search Works' report;
When digging down into Google's 'How Search Works' report, it reaffirms many of the factors that influence page rank and how that translates, when combined with the other key SEO Ranking Factors, into the SERPs. Some key factors that are part of On-Page SEO are as follows:
On-Page SEO Ranking Factors
Meta Title / Title Tag
Be sure put targeted keywords into the <title> tag of every page on your site, making sure they're relevant to the page content. Much like a book in a library, where the title appears on the spine of the book, the 'title' should very clearly show what the page is about. The title should be unique as it's text that's displayed on SERPs and user browser tabs.
The <description> tag shows directly below the title on SERPs. It's your opportunity to describe what the page is about, with a view to giving users a reason to click your link in the SERPs. Think of choosing a book to buy, before you buy it, the chances are you'd flip it over to read the description on the back cover - the <description> tag on a website is effectively doing the same on the SERPS.
Every page on your site should have a unique <h1>heading</h1>, which describes what the page is about - make sure you only use one <h1> per page. For other content areas in the page, if they need a title, you can use other heading tags (h2, h3, h4, h5, h6) but they should be in a hierarchical order. That is, don't lead with an h3 title, then use h2 inside the same content block.
Wherever possible, use keywords your site URLs. Keep them concise and avoid joined words and underscores, E.g. 'great-url', 'not_great_url', 'worseurl'. For more info on site URLs, refer to our page on URL Structure and SEO
For various queries, search engines rank more recent content better than older content, which means that regularly creating new relevant content can give you a ranking advantage for certain keywords. It is also understood that if your content doesn't change for a given period, the search engines will reduce their crawl rate of your site. If, next time they visit, your content 'still' hasn't changed, it's likely the gap between crawler visits will widen further. Keep adding fresh content, it helps with your SEO.
The search engines are improving their ability to detect automatically generated content (AI content) and are also removing content that has been copied from other websites from their SERPs. Keep your content fresh and original. More info on content quality can be found on our Optimised Content page.
Use of Target Keywords
Considering the above quote from Google's 'How Search Works' report, it's patently obvious that the use of target keywords and keyphrases will have a positive impact on your On-Page SEO. More info on this topic can be found on our Target Keywords page.
Alt text for images (alternate text)
This 'alt text' isn't visible to the most users, but it is used by screen reader apps to aid blind and partially sighted users understand what your images are. The search engines use 'alt text' when crawling images, so adding relevant keywords will help them understand what the images are and their relevance to your page content. Correctly naming images with 'alt text' helps 'Accessibility', which is an indicator metric for SEO, so very worthwhile to do this.
This is a huge part of your overall SEO strategy. Whilst it's technically part of 'On-Page SEO', Technical SEO is widely acknowledged to be a type of SEO in its own right. More info on Technical SEO.
Other SEO Ranking Factors to Consider
Optimising your On-Page SEO is obviously very important, but unless you get the other critical ranking factors right, your website and pages could remain a well kept secret. There are many other SEO ranking factors, but be sure to act on the Top 20 SEO Ranking Factors as an absolute minimum.