Letterpad uses react-helmet to take care of SEO. You can read more about the library over here . There is a helper component SEO.js which has some boilerplate to take care of default data. To add SEO, lets say in your SinglePage.js, simply make the component render along with the below tag and it will automatically set up the appropriate meta tags in the head of your document. It does the same while rendering on the server.

<SEO
        schema="BlogPosting"
        title={post.title}
        description={post.excerpt}
        path={"/post/" + this.props.match.params.slug}
        contentType="article"
        category={categories.join(",")}
        tags={tags}
        image={post.cover_image}
        settings={this.props.settings || {}}
 />