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To start an HTML5 engagement
Scoping through first sprint
100%
Senior engineers, US-based
No offshore handoff
Every sprint
Working software on a preview URL
Not a status deck between milestones
100%
Code and repositories you own
From the first commit
What HTML5 actually added
The elements and APIs that replaced a decade of plugins and workarounds
HTML5 wasn't a branding refresh over HTML4 and XHTML — it standardized a set of capabilities the web had previously needed Flash, Silverlight, or third-party libraries to fake.
Semantic elements
`<header>`, `<nav>`, `<main>`, `<article>`, `<section>`, and `<footer>` replaced generic `<div>` soup with markup that describes what a region of the page actually is — information search engines and screen readers both rely on directly.
Native audio and video
`<audio>` and `<video>` elements play media without a plugin, with a standard API for controls, captions, and playback events — the reason embedded video no longer requires a Flash player most browsers had already started blocking by default.
Canvas and SVG
`<canvas>` gives scriptable, pixel-level drawing for charts, games, and generated graphics; SVG gives resolution-independent vector graphics that stay sharp at any zoom level. Choosing between them is a real technical decision, not a style preference.
Offline and local storage APIs
`localStorage`, `IndexedDB`, and the Service Worker API (which underpins offline support and installability) let a web page retain data and function without a live network connection — the foundation Progressive Web Apps are built on.
Richer form controls and validation
Input types like `email`, `date`, `number`, and `tel` bring the right keyboard and built-in validation on mobile without a line of JavaScript, and the Constraint Validation API standardizes error handling for the rest.
Web Components
Custom elements, Shadow DOM, and HTML templates let a team build reusable, encapsulated components in standard HTML5 and vanilla JavaScript — no framework required, and usable inside one if you already have it.
What's involved
HTML5 engagement types
What moves the scope is less about page count and more about how much of the existing markup is semantic and accessible today, and whether the target is a new build, a rebuild, or an audit of something already live.
| Engagement | Commitment | Timeline | What's included |
|---|---|---|---|
| Semantic & accessibility audit | Fixed scope | 1 – 3 weeks | A page-by-page review against current WCAG guidance and semantic-markup standards, with a prioritized fix list. |
| Marketing or content site build | Fixed scope | 3 – 8 weeks | Hand-built, semantic HTML5 and CSS for a site that doesn't need a JavaScript framework's runtime cost, tuned for load speed and Core Web Vitals. |
| Progressive Web App conversion | Fixed scope | 4 – 10 weeks | Service worker, web app manifest, and offline caching strategy added to an existing site so it installs and works without a live connection. |
| Legacy Flash or Silverlight replacement | Fixed scope | 3 – 10 weeks | Interactive or media-driven content rebuilt in HTML5's Canvas, SVG, and native video, without the plugin dependency. |
| Ongoing support & maintenance | Ongoing retainer | Ongoing | Accessibility regressions, browser-compatibility fixes, and content updates handled on a standing basis. |
Ranges assume US-based senior engineers and include accessibility testing rather than treating it as a separate line item a cheaper quote often drops.
Semantic markup
Semantic HTML5 is an SEO and accessibility decision, not a formatting one
Search engines and assistive technology both parse a page's structure, not just its visible text. Markup that ignores that structure is invisible to both in ways a sighted user browsing normally would never notice.
Heading structure carries real weight
A single `<h1>` per page and a heading hierarchy that actually nests — `<h2>` under the section it belongs to, not chosen for font size — is one of the cheapest, highest-leverage SEO decisions on a page, and it's the first thing both crawlers and screen readers use to build an outline.
Landmark elements replace guesswork
`<nav>`, `<main>`, and `<aside>` let a screen-reader user jump directly to the page's navigation or main content instead of tabbing through every link in the header first. That's not a nice-to-have — for a keyboard or screen-reader user, it's the difference between a usable page and one they abandon.
ARIA is a supplement, not a substitute
ARIA attributes exist to describe interactive widgets HTML5 has no native element for — a custom dropdown, a tab panel. The first rule of ARIA is to use a native semantic element instead whenever one exists; reaching for ARIA before semantic HTML5 usually means covering for markup that should have been simpler.
Alt text and form labels aren't optional metadata
Meaningful `alt` attributes on images and explicit `<label>` elements tied to form inputs are both a WCAG requirement and a direct SEO signal — and they cost nothing to include from the start of a build, unlike retrofitting them across hundreds of existing pages later.
HTML5 under a framework
The layer every React, Vue, and Angular app eventually renders into
A framework changes how the markup gets generated. It doesn't change what a browser, a crawler, or a screen reader actually receives — which is still HTML5, and still judged by the same standards.
Frameworks don't exempt a page from semantic markup
A React component tree that renders nothing but nested `<div>`s produces the same accessibility and SEO problems as hand-written div soup — the framework doesn't fix bad markup, it just adds a build step in front of it.
When hand-written HTML5 beats a framework
Marketing pages, documentation, email templates, and content that rarely changes interactively are almost always faster and simpler as plain HTML5 than as a single-page app — no hydration step, no client-side JavaScript required just to display text.
Core Web Vitals are mostly a markup problem
Largest Contentful Paint is usually decided by how the hero image or text block is marked up and loaded, not by framework choice, and Cumulative Layout Shift is almost always fixed by giving images and embeds explicit width and height attributes so the browser reserves their space before they load.
Progressive Web Apps live at this layer
A web app manifest and a service worker — both HTML5-era additions — are what let a site be installed to a home screen and keep working offline, without the app-store review cycle a native app requires. It's the right call for content and workflow apps that don't need deep platform APIs; see our mobile page for when a true native or React Native build is the better answer instead.
Cross-browser and cross-device
Support for every browser your users are actually on, not every browser that exists
HTML5 support across current browsers is close to universal now, which removes most of the plugin and polyfill overhead earlier web development carried. What's left is testing discipline, not guesswork.
Graceful degradation over a lowest-common-denominator build
We build to modern HTML5 and CSS by default, and add fallbacks only where your actual analytics show a real audience on an older browser — rather than shipping a heavier, more conservative build to every visitor because some browser somewhere might need it.
Responsive images are a markup feature, not just CSS
`srcset` and the `<picture>` element let the browser choose the right image resolution for a device's screen and connection, cutting mobile page weight without a separate mobile site to maintain.
Real-device testing, not just a browser's simulator
A desktop browser's responsive mode catches layout bugs. It doesn't catch the touch-target sizing, viewport quirks, and font-rendering differences that only show up on an actual phone, which is why device testing stays in the plan rather than the CI pipeline alone.
Mobile is the default assumption, not an afterthought
Most web traffic today arrives from a phone or tablet, so layouts are built mobile-first and enhanced upward for larger screens — not designed for desktop and shrunk down as an afterthought once a client asks why it looks broken on their phone.
Related
Related services
What HTML5 work usually connects to.
Questions
Common questions about HTML5 development
What teams ask before a first call.
HTML5 is the current version of the markup language every web page is built on. It replaced the stricter, XML-based syntax of XHTML with a simpler standard, and it added semantic elements (`<header>`, `<nav>`, `<article>`), native audio and video, Canvas and offline storage APIs, and richer form controls — capabilities the web previously needed Flash, Silverlight, or a plugin to fake.
Every current browser supports it, which is a large part of why plugin-based web content has mostly disappeared over the last decade.
The main driver isn't page count — it's how much custom interactivity, semantic and accessibility work, and responsive design the site needs. A marketing site built in hand-written HTML5 is a smaller build than a Progressive Web App with offline support and a service worker, and a full accessibility audit and remediation on an existing site is priced separately from either.
A short scoping conversation about what the site actually needs to do gets you a real number faster than any general range.
Yes. A PWA is built on HTML5-era capabilities — a web app manifest that makes a site installable to a home screen, and a service worker that caches assets so the app keeps working offline or on a poor connection. It's a strong option for content and workflow apps that want an app-like experience without an app-store review cycle.
It isn't the right answer for everything — an app that needs deep platform APIs like background location or full offline data sync usually still wants a native or React Native build, and we'll say so if that's what your product needs.
For a lot of sites — marketing pages, documentation, content that doesn't change interactively — hand-written HTML5 and a small amount of vanilla JavaScript is faster to build, faster to load, and simpler to maintain than a full framework. A framework earns its runtime and build-tooling cost once the interface has deeply interdependent state: a dashboard, an editor, a real-time collaborative tool.
We'll recommend based on what the page actually needs to do, not default to a framework because it's the more common starting point now.
An HTML5 developer builds the markup and structure a page is made of — semantic elements, forms, embedded media, and the accessibility attributes that make a page usable with a screen reader or keyboard alone. On most projects that work sits alongside CSS for layout and styling and JavaScript for interactivity, rather than existing in isolation.
On a framework-based project, the same skill set shows up in making sure the framework's rendered output is still semantic, accessible HTML5, not just visually correct markup.
Yes. We start with an audit against current WCAG guidance — heading structure, color contrast, keyboard navigation, form labeling, alt text, and ARIA usage where a native semantic element doesn't already cover the case — and prioritize fixes by real impact rather than a flat checklist.
Most of what a WCAG audit finds traces back to non-semantic markup in the first place, which is why building semantic HTML5 from the start is cheaper than retrofitting accessibility onto a finished site later.
We build to current HTML5 and CSS standards by default and add fallbacks only where your actual traffic shows a meaningful audience on an older browser, rather than shipping a heavier, more conservative build to every visitor by default. Responsive images (`srcset`, `<picture>`) and mobile-first layout handle most of the device variation without a separate mobile build to maintain.
We test against real devices as well as browser emulators, since touch-target sizing and font rendering are two of the most common gaps a desktop simulator misses.
Yes. Interactive content, animations, and embedded media built on Flash or Silverlight can be rebuilt using HTML5's Canvas for scriptable graphics, SVG for vector art, and native `<video>` and `<audio>` elements — without the plugin dependency that most current browsers have already dropped support for entirely.
The scope depends on how much of the original functionality has to be reproduced versus reimagined for a modern, touch-friendly interface, which is usually the more valuable outcome of the migration anyway.