Someone fills your contact form on the train. Signal dies mid-submit. They tap Send anyway. On most WordPress sites, that message is gone. On a Progressive Web App that only caches pages to read, the form still dies. Reading offline is useful. Writing offline is the part most PWAs skip.
This post is about the write path: comments, contact forms, surveys, and some cart actions that can wait in the browser and fire when the network returns. Not payments. Not a fake “order placed” screen. A queue.
If you want the broader offline reading and checkout honesty angle, we already covered that in A WordPress PWA offline strategy that does not break checkout. Here we zoom in on forms and Background Sync inside Progressify.
The gap: cache-only PWAs vs forms that still send
A lot of WordPress PWA setups stop at “pages someone already opened stay available with no signal.” That is the read cache. Fine for a blog post. Fine for a product page someone browsed while online.
It does nothing for a POST. Comment box. Contact form. Survey. WooCommerce cart action. Those need the network. When the network is missing, a normal site either hangs, errors, or silently drops the data.
Background Sync flips that. The service worker holds failed offline requests and replays them once connectivity returns, in the order they were made. Progressify’s product page puts it plainly: comments, form submissions, and cart actions taken offline are queued and replayed when the connection comes back. Held in the browser. Not lost on reload.
That is the difference between “you can still read” and “you can still participate.”
What Progressify Pro actually does for offline forms
Two related Pro pieces work together. Know which is which.
Offline forms (Offline Usage tab). Visitors can submit forms while offline, with their consent. The submission is stored locally and sent automatically once the connection returns. Docs call out the obvious wins: comments, contact forms, surveys. They also spell out the hard limit: do not rely on it for anything that must succeed or fail immediately, such as a payment, because the visitor is told the submission was accepted before your server has seen it.
Background Sync (App Capabilities tab). Holds requests that failed because the device was offline and replays them once connectivity returns. This is what makes offline forms reliable. It is mostly a Chromium feature. Safari and Firefox implement little of it. Enabling it costs nothing where unsupported, but do not build a workflow that depends on it alone.
Same story on the product side: Background Sync covers comments, forms, and WooCommerce carts. Queue. Replay in order. No magic for card capture.
There is also a Pro offline connection indicator. Without it, an offline visitor may not understand why things stopped working. Turn it on if you expect people to use the site in tunnels and on patchy mobile data.
Consent, expectations, and what you must not fake
Offline submit only works cleanly when the visitor knows what happened.
They should consent to storing the submission locally. They should understand it will leave the device later, when the network is back. They should not think your server already received it as a final server-side success for money-critical flows.
That last point is non-negotiable. A contact form can say “we’ll send this when you’re back online.” A comment can wait. A survey answer can wait. A payment cannot. If your UI reads like “paid” or “order confirmed” before the gateway ran, you own the support ticket and possibly the chargeback.
Use offline forms for delayed-ok actions. Keep checkout and payment network-dependent. That split is how you get the PWA win without lying.
How to set it up on WordPress (practical steps)
You do not need a custom service worker. Progressify registers one built on Workbox. You configure behavior in settings.
1. Get a working PWA base first
Install Progressify. Fill in the web app manifest basics (name, icons, colors, display). Confirm the site is installable. If you are new to the category, start with What is a Progressive Web App (PWA)? A plain-English guide for WordPress site owners in 2026. Offline forms sit on top of a real service worker, not a theme trick.
2. Leave caching on Network-First
Under Offline Usage, leave the caching strategy on Network-First unless you have a clear reason not to. Network-First tries the network, caches the response, and falls back to the last cached copy if the request fails. Content stays current. Offline still works for pages already seen. Cache-First and Cache-Only will serve old pages after you publish until expiration. Bad default for news, stores with changing prices, or anything time-sensitive.
Offline forms are not a reason to flip the whole site to Cache-Only. Reading strategy and write queue are separate decisions.
3. Add a branded offline fallback
Pro. Point Offline Fallback Page at something like /offline. Keep that page self-contained. Few external fonts. No page-builder stack that needs six uncached scripts to show a headline. Say what happened. Offer something useful (sections they already visited, a retry tip). A browser dinosaur page is not a brand moment.
4. Turn on the offline connection indicator
Pro. When the connection drops, show it. When it returns, clear it. People stop blaming “your broken site” when they can see they are offline.
5. Enable Pro offline forms with consent
On the Offline Usage tab, enable offline form submission. Make sure your UX asks for consent and sets expectations: stored on this device, sent when online again. Useful for comments, contact, surveys. Not for payments.
6. Enable Background Sync
On App Capabilities, turn on Background Sync so failed offline requests replay when connectivity returns. Test on Chrome or Edge first. On Safari and Firefox, treat support as limited. Have a graceful path for browsers that do not implement it: the setting costs nothing where unsupported, but your product story should not assume every visitor gets the queue.
7. Treat form autosave as a different switch
Pro form autosave saves what a visitor typed before submit and restores it on reload. Valuable on long forms and comment boxes. It keeps the saved values even after a successful submission. Leave it off for most forms, or the next person on a shared device sees the last person’s answers. Offline queue and autosave solve different problems. Do not confuse them in your admin notes or client handoff.
8. Airplane-mode test the write path
Open the site online. Load the form page. Go offline. Fill and submit with consent. Confirm the UI queues rather than faking a server success for money flows. Come back online. Confirm the request replays. Check comments, contact, and (if relevant) cart actions separately. Then open checkout offline and confirm it does not pretend payment worked.
Pitfalls that burn people
Building the whole funnel on Background Sync alone. Chromium-heavy. Safari and Firefox limited. Fine as an enhancement. Bad as the only path for a mission-critical lead form on every device.
Offline “accepted” language on payments. Docs are explicit. The visitor can be told the submission was accepted before the server sees it. That is fine for a survey. Catastrophic for cards.
Cache-First because a comparison table said “faster.” You get stale content and confused editors. Network-First is the honest default. Pair it with a write queue for forms that can wait.
No offline indicator. Visitors think the form is broken. They bounce. They leave a one-star review about “site doesn’t work on mobile.”
Autosave left on for shared devices. Library computers, storefront kiosks, family tablets. Next visitor sees prior answers. Turn it off unless you know the context.
Expecting never-opened pages to work offline. Only pages the visitor already loaded are in the cache. A never-seen URL correctly shows the fallback. That is not a bug.
Stacking a second service worker. Two PWA plugins, or a hand-rolled worker beside Progressify, fight over the same scope. Pick one layer.
Skipping consent. Storing form data locally without a clear OK is a trust and compliance problem. Progressify’s offline forms path is built around visitor consent. Use that framing in your copy too.
Where this fits in a real WordPress product
Content sites and blogs. Offline reading plus queued comments is a retention feature. People finish the thought on the commute home.
Lead-gen and service businesses. Contact and survey forms that survive a dead spot mean fewer lost inquiries. Still confirm important leads server-side when they land.
WooCommerce. Cart actions can queue. Payment confirmation cannot. Keep money paths honest. Use Background Sync where delayed success is acceptable, not where a gateway must answer now.
Membership and courses. Lesson pages already opened can stay readable offline. Forms and comments can queue. Login and entitlement checks stay on the network.
Progressify, Pro, and the membership
Progressify is DaftPlug’s all-in-one Progressive Web App plugin for WordPress. Free on WordPress.org for the core PWA path. Pro unlocks the deeper offline story: branded offline page, offline connection indicator, offline forms with consent, Background Sync, form autosave, app-like UI, richer push, optional Android and iOS bundles from the same site, and the rest of the paid set.
You do not buy Progressify Pro as a lonely line item forever. One DaftPlug Pro licence unlocks Progressify plus Lightify (performance), Rankify (SEO and GEO), Generatify (AI), and Snapshotify (backups). New Pro plugins join existing memberships. Plans differ by site count, not by feature list. Prices and tiers live on pricing. There is a 14-day money-back guarantee if it is not a fit.
If you were about to duct-tape a cache-only PWA, a separate form plugin “offline mode,” and a custom worker, compare that pile to one membership that already ships the write queue and the read cache in the same product.
Takeaway
A WordPress PWA that only caches pages for reading is half a product. Offline forms plus Background Sync close the other half for actions that can wait: comments, contact, surveys, some cart actions. Consent first. Replay in order when the network returns. Never dress a queued request as a paid order.
Leave caching on Network-First. Add a branded fallback and an offline indicator. Enable Pro offline forms and Background Sync where Chromium visitors will benefit. Keep payments on the live network. Test in airplane mode on purpose.
That is how Progressify turns “works offline” from a reading demo into something people can actually use when the signal drops. One Pro membership covers Progressify and the rest of the DaftPlug line. Ship the queue. Keep the checkout honest.