Behind the scenes: photo sharing on SkyDrive

Behind the scenes: photo sharing on SkyDrive

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When we launched Windows Live SkyDrive in August of 2007, we had the clear goal to make sharing easier and better for anybody on the Internet. But offering free storage to the world is a risky proposition – the list of services that have tried to do this and failed is long. So we took it slow, starting only in the US, offering just 500MB of storage at first, and focusing on a basic experience for uploading files. Over time, as we learned more about usage (and learned more about how to thwart various types of scammers and other evil people), we were able to increase the free storage, first to 1 GB, then 5 GB, and finally about a year ago to 25 GB of free storage. We were also able to expand into new markets. Today we’re in over 50 languages worldwide and more than 50% of our customers come from outside the US.

Of course, “making sharing easier and better” is a broad goal – and we’re not going to achieve it overnight. So, after getting the basic infrastructure built, we turned our energy to sharing photos. Looking around the Internet, it seemed like every week there was a new website or application that helped people share photos. Many of these services came and went, while a select few have managed to stay around. We thought that the last thing the world needed was another “me too” photo sharing service, so we chose to focus on a few unique scenarios:

  • Enabling the highest quality photo sharing possible
  • Fixing the problems inherent in group activities – where lots of people take photos and want to share them together – like birthdays or football games
  • Giving easy and complete control over privacy – who can view and edit your photos

I’ll take you through these one by one and talk a bit about how they work.

High quality photo sharing

People have lots of choices for sharing photos, but sometimes you really want to share photos using the highest possible resolution, for printing or just to store a permanent copy of the original. Most of the time, users are just quickly sharing photos, so by default we resize photos to 1600x1600 pixels, allowing them to upload more quickly. But when you want to, you can easily choose to upload the original files (up to 50 MB per file).

From the customer side, it looks easy, as it should. But behind the scenes, there's a lot more going on.

First, because your memories are priceless, every time you upload a photo, we actually store four copies of it on our servers. Hardware failures are extremely rare, but because we're storing billions of photos, even extremely rare things happen occasionally. Multiple copies of each photo allow us to quickly recover when these infrequent events occur – you simply never need to worry about this. Of course, these four copies don’t count against your free 25 GB.

It’s great that you can upload huge photos, but we want your web experience to be lightning fast, so the next thing we do after making sure we have four safe copies of each photo is create nine smaller versions of each photo, which we use for everything from thumbnails to large slideshows. Here is how that breaks down.

We create six smaller versions that preserve the aspect ratio of the photo (so the photo stays portrait or landscape just like you took it).

  • 800 x 600 px max. - for web slideshows
  • 600 x 450 px max. - for single photo view
  • 320 x 320 px max. - for large mobile phones
  • 176 x 176 px max. - for small mobile phones
  • 96 x 96 px max. - large thumbnails for the web
  • 48 x 48 px max. - small thumbnails for the web

We also create three smaller versions where we use some smart code from Microsoft Research to do a square crop that contains the more interesting part of the picture. We use these in places where a square thumbnail makes for a prettier and more usable layout (like the big list of photos inside of a photo album).


These sizes are:

  • 213 x 213 - large square thumbnails
  • 104 x 104 - medium square thumbnails
  • 48 x 48 - small square thumbnails

So every time you upload a photo, we actually store four copies of every original, plus nine additional sizes (none of which count against your 25 GB of storage, of course).

Group activities

The next thing we focused on is a classic problem that many of you have probably encountered. You go to a party (or football game or weekend trip with some friends) and afterwards you want to share your photos with them, but you also want to get their photos. People we talked to in our research told us that they usually handled this is by trading memory sticks or trying to remember to email each other with photos. But there's got to be a better way, right?

So we made it super easy in SkyDrive to give other people permission to add photos to a shared album. Now all you have to do is create the album, and then when you share that album with friends, give those same friends permission to add photos. Now everybody can add their own photos and tags, and comment on the shared collection. When you’re done, you can download all the original quality photos in a single ZIP file, or you can import them directly into Windows Live Photo Gallery.


And of course because you can share high resolution photos – you never have to send email to a friend asking them to send you the original of that great picture of you from your ski trip. You already have it. And if you are a photography geek and like taking photos in RAW mode (a special mode unique to each camera that has higher quality) you can upload those RAW files in addition to the normal JPG files.  


Of course none of this matters if you aren’t in control of your stuff. People are increasingly concerned about privacy on the Internet, particularly with photos. So we’ve focused on giving you all the control – and at the same time making it super simple to create and share with the people you want.

Whenever you create a photo album you can easily choose who has access to your albums. We have easy default options for who can see the album: just you, your entire network, or everyone (public). In addition, you can also easily choose individual people (regardless of their email address) and we will give just those people access to the album.


And when you give people access, you have a lot of control over what kind of access they have – for example, you can make everything read-only, or allow people to add and delete photos. And you can control whether people can add comments and people tags as well.

These options help you make sure you're never surprised by who can see or modify your photos – you're always in control.

Adding it all up

We’ve had a lot of fun building SkyDrive so far. We’ve been thrilled to have so many of you find and use SkyDrive. To give you a taste, in the last year we’ve had a little more than 2 billion photos uploaded to SkyDrive and shared with hundreds of millions of people. On a normal day we usually see between 4 and 5 million unique photos! And when you remember that we turn each of those photos into four full-resolution copies and then nine additional smaller versions – that’s around 65 million photos per day that we store for you.

Of course, we have lots more ideas about photos - including some neat things we’ll announce in the coming months. Plus, for the last six months we’ve been running a technical preview for Office Web Apps on SkyDrive– if you haven’t seen it yet, check it out. This is just the tip of the iceberg for storing documents on SkyDrive – we’ve got a lot more coming.  But I’ll save that for a future post.


Eric Doerr
Group Program Manager
Windows Live SkyDrive, Sync, and sharing

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  • danielgr
    73 Posts

    @ Eric

    Yeah, I've certainly noticed Windows Live Movie Maker. I don't use it myself because I prefer more advanced programs, but to me it's really good in the sense that even my father manages to make his own decent videos using it. The problem right now is that he has no real choices to share them with us, because available options (like youtube) aren't as easy/flexible on rights managements as Skydrive and Windows Live Groups. My father doesn't want to have a facebook account, nor does he want to upload their videos for anyone to watch, nor does he care at all about all the social networking. For us I've created a Windows Live Group for the family so that everyone can easily upload their photos and stuff without caring about "who will be able to see this/that?".

    So far though, he uploads the videos as simple files to skydrive, which are a real pain because one has to download them to even guess what are they about.

    On Picassa online you can upload videos that will play streaming straight away, and that's certainly the kind of feature I'd like to see in Windows Live Skydrive rather sooner than later.

  • @ danielgr - Thanks for all the feedback. Here are some thoughts.

    Re: Active X - Yeah, we work hard to support a broad range of scenarios across the major browsers, but this is a place that only works on IE. We look at this regularly, so thanks for the feedback.

    Re: Upload - We've love to work with Picasa (or any other app) to support upload to SkyDrive. They just have to decide that they are willing to give their customers that choice.

    Re: Video - We're 100% with you. Videos are the new photos. In case you haven't seen, we've been spending a lot of time on Windows Live Movie Maker ( This is definitely an area we're watching closely.

  • danielgr
    73 Posts

    Actually, many people miss the pretty nice multiple file upload tool simply because the active X control only works with Internet Explorer. As such, people using Firefox or other browsers can't use it.

    As for interoperability, I don't know who is to blame, but I do know that you can use Windows Live Photo Gallery to upload photos to many internet services (including SkyDrive, but also Google's Picassa or FlickR), whereas I can't use Picassa's software to upload to SkyDrive.

    Btw, one of the things that I've really been missing on SkyDrive is the possibility to add streaming video. That should certainly be possible by using Microsoft's own Silverlight tech, and it's certainly one of the things that I prefer from Picassa online galleries. Hate how the later loses my metadata and ask me to pay for extra storage though...

    Anyway, I sure hope Microsoft people have noticed that video is becoming more and more popular as far as sharing "our life experiences" go, and that not everyone wants to put their family/private videos on youtube. It'd be great if Windows Live provided such service, given the fact that the storage capacity is already there.

  • @7flavor @gcoupe - We spend a lot of time making sure that we interop well with other photo editing and management tools in the industry. This is why we preserve metadata on roundtrip to the service, and why we worked hard with Adobe to standardize on XMP for most metadata (of course we also support EXIF and IPTC too). In the few cases where we have added custom metadata (like people tag regions) we've blogged about the extensions we've made so that other tools (like Picasa) can choose to support us if they like.

    @Drazick - We have an ActiveX control that allows drag/drop and multiple file upload from the browser. Have you tried that?

  • Drazick
    16 Posts

    What we really need is Multiple File Upload Wizard.

    Please make use of "File API" instead of Flash / Silverlight.

  • You know, I find it somewhat depressing that a Group Program Manager for Windows Live SkyDrive, Sync and sharing doesn't even mention the fact that the service preserves image metadata. Either he's unaware of it, or he thinks it's unimportant.

    If it's the former, then that really is depressing, and if it's the latter, then he's very mistaken.

  • 7flavor
    352 Posts

    Yeah but we need integration for other apps not just Photo Gallery. Like maybe a Picasa button to export to SkyDrive. Does SkyDrive allow downloading batch photos into Picasa? So much interoperability.