Features
What is offline mode in an app?
Offline mode is an app’s ability to keep working when the phone has no connection: showing the data a person needs, accepting what they enter, and holding it on the device until a signal comes back. It’s two pieces of work, storing locally and syncing back, and the second needs decisions only you can make.
- $38,000 – $54,000
- A customer app that needs a connection
- $48,000 – $68,000
- The same app, working with no signal
- $10,000 – $14,000
- What offline adds, storing and syncing together
Measured against the estimator’s reference build: a customer app for iPhone and Android with accounts, two kinds of user, notifications, document uploads, and a web page for the office, with nothing built behind it yet.
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WhatWillMyAppCost
We build the estimator this site runs on, and we design and build custom mobile and web software for a living. Every figure on this page is the estimator’s own output.
How does offline mode work?
The app keeps a copy of what the person needs on the phone, lets them work against that copy, and writes their changes to a queue that uploads when the connection returns. Five parts, and a customer sees none of them.
A local copy. The records this person will need today, downloaded ahead of time, so the screen isn’t blank in the basement.
A queue. Every change made offline, in order, stored so it survives the app being closed or the phone dying.
Retries. Uploads that failed halfway try again without sending the same record twice.
Status. A quiet sign that their work hasn’t gone up yet.
Conflicts. What happens when the record they changed was changed by someone else in the meantime.
Which data to hold is a decision about the job. A technician needs today’s jobs and the customers on them. They don’t need every record since the company started, and the app is sized by that choice.
Why is syncing the hard half?
Because the office kept working while the phone was out of range. When the phone comes back holding a changed record and the server already has a newer one, somebody decides whose version stands, and that’s a business rule before it’s code. The background sync page walks the cases, and the offline guide prices them on an app that already exists.
Storing data locally is the easy half. The hard half is deciding what happens when two people edit the same record on different devices and one of them was in a basement for six hours. Offline also has to be tested on bad networks, not just no network.
What does offline mode cost?
$10,000 – $14,000 on the reference app, which prices at $38,000 – $54,000 when it can assume a connection and $48,000 – $68,000 when it can’t. The timeline moves from 14–20 weeks to 15–22 weeks.
- $6,000 – $7,000
- Storing on the phone, by itself
- $10,000 – $14,000
- Storing and syncing back, together
Run the description with offline in it. It’s filled in already, and the only change from the reference build is one sentence about rural coverage.
If the answer to “where is it used” includes a basement, a job site, or a rural route, say so in the first paragraph of the brief, and the number will include it. That’s a new app. On an app that already exists, the server sets the price more than the app does, and the offline guide prices that case.
Offline mode or background sync?
To the person using it, it’s one feature. To the people building it, it’s two. Offline mode is the holding; background sync is the getting back. They’re priced as separate features, and sync comes on with offline unless you switch it off.
- Offline mode
- Working against a copy on the phone. What the person sees and enters when there’s no signal.
- Background sync
- Moving that work to the server, and the office’s changes back, once there’s a bar, without losing or doubling anything.
A technician in a crawl space is the usual case. The field service guide is built around that person and prices offline on a tech app.
Offline mode is the part of an app that keeps working with no signal: it holds what the person needs on the phone, accepts what they enter, and sends it up when the connection returns. Holding the work is the straightforward half. Getting it back is the half with decisions in it. On a $38,000 – $54,000 customer app, the pair adds $10,000 – $14,000.
Questions people ask next
Which apps need to work offline?
The ones used where the signal isn’t: basements, job sites, rural routes, and buildings with thick walls. If yours is used in offices and homes on a normal connection, say so, and the estimator prices nothing for offline.
Can offline mode be added later?
Yes. It costs more than building it in, because screens written for an always-online phone get reworked and the server has to change too. The offline guide prices that case on an app that already exists.
How does the app know what to show with no connection?
It shows what it last downloaded. Part of building offline mode is deciding what to download ahead of time, for whom, and how old it can be before the app warns the person it may be stale.
Is “works offline” the same as “works when the signal is bad”?
No, and the second is harder. No signal is a clean state: hold everything and wait. A bad signal means uploads that start and die, which is where records get lost, so the app is built and tested for both.