Apps are the cornerstone of iOS. The ecosystem is what sets Apple's mobile platform apart from its rivals, and the highest-quality iPhone apps are typically best in class.
But, like any app store, it is sometimes difficult to find out what are truly the best apps, the ones that stand out from the rest - because they offer a tool or service that is far beyond anything else available.
Sometimes the best apps are free, other times you will have to pay a little bit for them. Here we showcase the best available and offer up everything you need to know about the app and how much it will cost.
This round-up compiles our favourites, from top-quality creative tools and video editors to the finest productivity kit and social networking clients and even if you don't have an iPhone right now it's worth reading up on what's available if you're considering investing in the iPhone 6S / iPhone 7 when it's out.
As always, if your essential app isn't on the list - let us know in the comments...
Air Video HD
Even the most expensive iPhone has a fairly limited amount of on-board storage and that's not even likely to change with the iPhone 7. This is a problem if you have a large video collection you'd like to access. Air Video HD server streams (and if necessary, re-encodes) files from a PC or Mac that can then be played on your iPhone; there's AirPlay support, and also the means to access your Air Video server over the web.
Byword is a text editor that hits the sweet spot of being both usable and simple. Its font is clear, and a toolbar adds live word count or Markdown buttons. Your documents can be saved locally, to iCloud, or to a linked Dropbox account. Output can also be exported to various formats (PDF; HTML; email) or to a blog if you buy the $4.99/£2.99 'Publishing' IAP.
Easily the most beautiful of the iOS stargazing apps, Sky Guide also happens to be the most usable. You can quickly and easily scan the heavens by dragging your finger around, optionally orienting the screen to wherever you happen to be looking. A Today view widget adds information about rise and set times for nearby planets, the sun and the moon.
Traditional journals are all very well, but there's something wonderful about an app that you always have with you, into which you can save messages, images, locations and more, and then later retrieve everything via a search. Day One is beautifully designed and easy to use - best-in-class on the iPhone.
Fantastical 2 betters iOS 8's iffy Calendar app by way of a superior interface, a non-hateful method of dealing with reminders, and truly exceptional event input. The app has a powerful parser, and so while adding an event, you can enter the likes of "TechRadar lunch at 3pm on Friday", watching a live preview build as you type.
Figure crams Reason's rich history of classic-era electronic music apps into a shoebox. Via a mixture of dials and pads, you can create all manner of banging choons, and then export them and assault your friends' eardrums. It's a fun toy for anyone, but also has the chops to be part of a pro-musician's mobile set-up.
Free with new devices or $4.99/£2.99
Camera enables you to do the odd bit of cropping with video files, but iMovie is an audacious attempt to bring a full video editor to your iPhone, infused with the ease-of-use its desktop counterpart is renowned for. Amazingly, it succeeds. Effects, themes, credits and soundtrack creation then provide extra polish for your mobile filmmaking.
Launch Center Pro
More or less a speed-dial for regularly performed tasks, Launch Center Pro can be a huge time-saver. You can create shortcuts for things like adding a new Tumblr post or sending your last photo to Twitter, and these shortcuts can be arranged in groups. An essential purchase if you heavily use even a handful of the supported apps.
Transmit for iOS
The app that defines iOS 8, Transmit for iOS is also a missing link for anyone who wanted a file manager for their iPhone. It might have roots in an OS X FTP client, but Transmit for iOS also integrates with cloud storage and local networked Macs. It's perfect for moving documents, renaming files, and creating archives to email or upload.
There are RSS readers that are more efficient, but Unread is the most pleasant to use. The interface begs you to sit back and take in articles from feeds you're subscribed to, and plentiful share options enable you to send content onwards. Note that although this is a free download, it's essentially for a demo; the full-price unlock gets you the regular app.
There are prettier and more stylish weather apps, such as Dark Sky (which we're also rather fond of), but it's WeatherPro that gets our vote, largely because of its accuracy. But it's also information-rich, with radars and detailed forecasts for your favourite locations.
Apple's Podcasts app has improved since its initial launch, but still falls short of Pocket Casts. The third-party app cleverly mixes elegance and character, with a friendly, easily browsable interface. Subscriptions can be filtered, and you can stream episodes of shows you've not yet downloaded.
Soulver eschews trying to recreate a traditional calculator on your iPhone. Instead, it's akin to jotting down calculations on the back of an envelope, but a magic envelope that pulls the numbers from your in-context sentences and gives you a total. Live currency conversion is built in, and you can save calculations and sync them via Dropbox or iCloud.
Originally the darling of the iPad, The Elements in late 2013 became a universal app, so it could be enjoyed on iPhones too. A rich, engaging digital book, it tells the story of the periodic table. Each of life's building blocks can be manipulated on the screen, before you delve into related facts and figures.
There are a lot of conversion apps about, but Vert 2 caught our eye through an interface that prizes clarity above all else. Beyond that, a combination of smart filtering and customisation cements the app's place on your home screen. And if you don't like the theme, you can easily make your own.
We've never been overly impressed with Apple's HDR, and it pales in comparison to vividHDR. The basic concept is the same: stunning, vibrant photos, capturing amazing details in both highlight and shadow. But vividHDR's combination of speed, presets and 'before and after' comparisons results in better photos - and that's what really matters.
If you don't feel the iOS Camera app really cuts it, ProCamera 8 should give you what you need: a bunch of extra modes (night; rapid fire; anti-shake; timers) and a dedicated lightbox with a range of editing features and filters. You can even buy vividHDR (see elsewhere in this list) as an IAP.
Apple's GarageBand remains an impressive, ambitious app, turning your iPhone into a recording studio. You get synths, loops, drums, guitar amps and a DAW for arranging MIDI data, making it suitable for beginners and pros alike.
With its huge range of amps and effects, ToneStack is an excellent choice for guitarists wanting to make some noise by connecting their instrument to their iPhone. An ABY unit enables you to split the signal, for hugely complex set-ups. And if that's not enough, a slew of IAP provides yet more amps, stomp boxes and features, including an eight-track recorder.
We elsewhere mention Byword as a great iPhone writing tool, but Editorial is *the* app for people who want to have a huge amount of control over creating and processing their output. The writing interface is strong, but what makes Editorial is the means to quickly add custom snippets and integrate workflows for extending the app and saving you time.
Bloom was originally released to much acclaim way back in 2008. A collaboration between Brian Eno and Peter Chilvers, the app's all about exploring generative audio through touch. The result is a relaxing noodly musical experience, and recent updates have fully optimised it for modern Apple kit.
On the Mac, OmniGraffle 2 is well known for being a first-rate tool for working on diagrams and wireframes. It's finally reached the iPhone by way of the iPad, and while the smaller screen makes the going a touch fiddly, this is best-in-class on Apple devices. It's pricey, but you get what you pay for.
There are tons of gimmicky effects apps on the App Store, but Fragment propels itself far beyond any also-rans through offering something strikingly different. Via some taps and twiddling, any photo can be turned into an explosion of mirrors, your own personalised kaleidoscope. Practical? Not really. Engaging? Most definitely.
For illustrators on the go, Procreate Pocket is a must-have. You get a big range of brushes, transform tools, a superb painting engine, and a full-featured layer system. Alas, there's no IAP for magically improving your digital painting skills.
Workflow is all about automation. You can download sets of actions or compose your own, which can trigger iOS apps and related services. For example, you could create a Home screen icon to call a friend, or build a single-tap icon to get directions to your nearest coffee shop.
Although iOS includes iCloud Keychain for securely storing/sharing login and payment details, 1Password is a better system. It's cross-platform, supports multiple identities and secure notes, and enables you to edit login details on your iPhone.
A pro mode IAP ($6.99/£4.99) adds multiple vaults for teams/families, categories for personal documents, tagging and custom fields.
BBC iPlayer is our favourite TV catch-up app because it cares about the user experience. There are no ads, you can watch live TV, and you can access content broadcast over the past 30 days. Episodes can be downloaded to watch later, and there's AirPlay support for sending shows to your telly by way of an Apple TV.
Should you find yourself in one of the supported cities (including Paris, London, New York and Berlin), you'll be grateful to have Citymapper on your iPhone — assuming you don't want to get lost.
The app finds where you are and then gets you from A to B, whether you want to walk, grab a taxi, or use public transport (for which live times are provided).
Until Apple sees fit to give us a Files app for iOS, Documents 5 will have to take the strain. It's really a document reader, designed for displaying PDFs, but in having full iCloud Drive access, it can be used to manage local and remote files, and download documents to your iPhone from the web.
There are plenty of solutions for transferring content between your computer and iPhone, including Apple's increasingly popular iCloud. Dropbox is still worth using, though. It has great cross-platform clients, integrates with iOS 8's Share sheets, and has direct support in many iOS apps.
Duolingo is entirely free from IAP, which is extremely generous given the quality of the app and its potential for helping you learn a new language.
It's packed full of bite-size quizzes that you can dip into at any time, and that gradually build your vocabulary and grammar in any of the ten supported languages.
Start using the eBay app and you won't go near the site on a PC again. It's fast, efficiently flags new finds based on your activity, and can be used to create new listings. The built-in bar-code scanner can save you loads of time with the last of those.
The idea behind Evernote is you should never forget anything again. Instead, you upload and tag everything, so the service becomes your digital memory. For free, you can upload 60 MB of data per month. Go premium ($5/£4 per month) and you can upload a gargantuan 4 GB per month, search document text, and store your notebooks offline.
Although Evernote Scannable is quite basic by iPhone scanner standards, it's also efficient and reliable. On launching the app, simply point your camera at a document that contrasts the surface behind it and the app will capture it. The JPEG can be sent to Evernote or shared via another service, and multiple scans are compiled to PDF.
Find My iPhone
Using Find My iPhone, you can always find where your device is, and keep track of any other devices on the same account. It's very useful if you've misplaced your device or think it's been stolen and want to know where it's at.
Apple's own Maps app has improved a lot since its botched debut, but Google Maps remains a must-download for any iPhone user. It's far superior than Apple's app for walking directions, has a street-level view, enables you to search local businesses, and for some cities includes public transport information.
The revamped Google Translate is an astonishing app. When online, it'll translate written, photographed or spoken text between a huge range of languages. And for English to French, German, Italian, Portuguese, Russian, and Spanish (and back), the app will try to live-translate whatever's in front of your iPhone's camera — even when you're offline.
When you've a sizeable music collection, you can get stuck in a rut and always end up listening to the same thing. Groove tracks your listening habits and cross-references the data with last.fm.
The result is a constantly evolving selection of automated personalised playlists, which might change your iPhone music-listening habits forever.
Instapaper was the service and app that kickstarted 'read later', the means to save web pages for later. Unlike Safari's Reading List, Instapaper strips articles back to just text and images, thereby providing an efficient and usable interface.
Premium membership ($2.99/£2.29 per month) unlocks the means to search your archive and add highlights to articles.
Movies by Flixter
Movies by Flixter is a simple, efficient app that figures out where you are, and then lists local cinemas, so you can check out what's on. Alternatively, you can select a film and the app will intelligently offer showtimes, enabling you to figure out where best to go.
For beginners keen on making music, Launchpad is perfect. You choose a genre and then trigger loops with a tap. Effects are only a further swipe and tap away. If you really get into the app, there's IAP for further loops and the means to import your own audio.
Now as synonymous with mobile exercise as Nike+, RunKeeper is an excellent app, backed by a robust social infrastructure. Using your iPhone's GPS, you can track exercise routes and then share activities with friends. IAP subscriptions are available for 'elite' users, and are ad-free and offer real-time sharing.
FaceTime is a great alternative to standard voice calls, but it only works with Apple kit. Skype remains the best widely-used alternative for people you know distinctly lacking in Apple devices.
You get free calls to anyone else using Skype, and cheap calls to anywhere in the world. If you're on Pay and Go, this can be handy, and the app enables iPod touch users to call normal phones too.
For the most part, social media is fleeting, but Timehop is all about digging up precious memories from the past. You link it to whatever social media services you frequent (and your on-device photos) and it shows you what was happening years ago on today's date.
TodoMovies is a to-do list for movies. Using the clean, efficient interface, you can check out what's on (and, if you like, movies from the past) and fashion a list of films you want to see.
Usefully, the app provides the means to rate every movie, and so extended use results in a list of favourites you can delve into at any time.
For free, TunnelBear VPN gives you 500 MB of private browsing that can worm its way around geo-locking. All you do is fire the app up and tell the bear where to tunnel. If you want unlimited data, it's yours for $2.99/£2.29 per month.
It's a pity Twitter has felt the need to hobble third-party clients, given that its own app doesn't appear to need any help these days in fending off the competition. Twitter for iPhone is fast and efficient, boasts useful Connect and Discover views, and expands tweets that contain photos, videos and other media.
You can do without most Today view widgets, but Vidgets provides some really useful monitoring tools.
The standalone app is where you manage your icon-like 'vigets', which comprise world clocks and indicators for storage and network speeds. That sole $2.99/£2.29 IAP is primarily for showing your support, but you do get an option for saving space by removing widget titles.
There are plenty of Wikipedia clients (free and paid) for iPhone, but Wikipanion is our favourite. You get quick access to article sections, in-article search, viewing options, and a location-based map search. The paid [Plus version](https://itunes.apple.com/en/app/wikipanion-plus/id290613987?mt=8) ($4.99/£3.99) adds article queuing and downloading for offline reading.
To some extent, Yousician Guitar is like Guitar Hero, only you use a real guitar that the app is teaching you how to play.
You start with basic plucking and strumming before moving on to working your way through full songs, the app scoring you as you go. For free, the app only restricts daily play time. To go unlimited, subscribe for $19.99/£14.99 per month.