320 x 568 is not an iPhone screen resolution, they started at 320 x 480. Maybe you are getting Android/Safari visitors? Since iPhone 4, the resolution increased to 640 × 960 and current versions have the same resolution as some desktop monitors. They retained the same aspect ratio through iPhone 4 and the resolution was increased to 640×1136 in iPhone 5. That is the same aspect ratio, but now it has higher ppi definition. Today's iPhones specs (from the Apple site: [apple.com...]

iPhone 6s
Retina HD display with 3D Touch
4.7-inch (diagonal) LED-backlit widescreen
1334-by-750-pixel resolution at 326 ppi
1400:1 contrast ratio (typical)

The 6s+ has 1920 x 1080-pixel resolution at 401 ppi. The screen aspect ratio has remained the same since iPhone 5. The resolution does not define the viewable window so screen resolution should not be a factor beyond using 360 x 480 or 320 x 480 to accommodate the oldest models. If you are coding for specific media queries, the resolutions can be set individually. If your layout accommodates multiple resolutions you can skip some steps.

Even a used iPhone can be pricey and AFAIK the screen resolutions on the iPod Touch are the same as their iPhone model-year. The iPod Touch has been discontinued. An Apple refurbished iPod Touch can be had at under $140 and that may be all you need. In my experience it is better to get an Apple refurb (with guarantee and new battery) than take a chance on someone's old problem. An old device might need a battery - that can be up to $200. Many phone carriers offer refurb iPhones, but they don't go back very far, maybe to iPhone 5.

Thanks for your reply.

I understand that the iPhone 4 was 320 x 480. However, for a high percentage of my traffic, Google Analytics is showing the browser, Safari with a resolution of 320x568 for a mobile device, so I am thinking this is a phone in the iPhone 5 series. Google chrome developer tools also lists the iPhone 5 as having a 320x568 resolution.

Anyway, I will take your comments on board. I have been taking a mobile first approach starting from 320 width and using media queries for higher resolutions. I was disappointed that a few things were not rendering on an iPhone as they looked in my browser using the Chrome Developer tools, hence my need to have an actual iPhone or Touch to test things out on.

I looked at my site on a 2nd gen Touch and it was terrible, but I figured this was more to do with an old browser and OS rather than my code (my site looks fine on a PC with modern browser, and on my android phone - Note 4).

I agree about the used price of iPhones I am quite surprised.. here in the UK they are even more expensive used.

[paintcodeapp.com...]

[edited by: Spyder_Cat at 7:41 pm (utc) on Sep 20, 2015]

320 x 568 is not an iPhone screen resolution,

Huh?
My stats show:
Browser/OS:iPhone/iOS
Mobile Device:Apple iPhone
Resolution:320x568

.

Sorry for any confusion. An iPhone 5 may show at a resolution of 320x568, it is not the same as a 320 x 568 screen due to device pixel ratios. If the device pixel ratio is 2:1 then 320 x 568 = 640 x 1168 so that means iPhone 5. Do the stats give you the device pixel ratio to calculate with or any other description of the device?

It looks like it is related to the stats provider, I don't see that size but I don't use GA for stats.

No problem. From what I can see, for mobile devices, Analytics doesn't give the device pixel ratio or the model info for Apple Devices (just 'iPad' or 'iPhone'). For Android devices the models are listed which can be helpful.

I've decided to buy a 5th generation iPod Touch. I just checked the Apple site and it will support the just released iOS9, so this device should last a while for my purposes. I've always been a PC/Android person so this is new territory for me :)

2nd thoughts I will go for the 6 gen Touch released July this year. If I pay a bit more and go for this one, there is more chance of IOS updates in the future.

not2easy;

device pixel ratio is 2:1 then 320 x 568 = 640 x 1168

Ahha! Thanks for the explanation.

The info I posted above came from Stat Counter.