Browser Add-ons, Mozilla, Mozilla Firefox, Programming, URL Fixer

My experience with developing a freemium browser add-on

Update: URL Fixer was acquired and is now hosted at

I have written twenty-six add-ons for Firefox in the last five years that I have released for free on Mozilla Add-ons. I enjoy writing add-ons, and because I wrote most of them to fulfill my own needs, I had no problem giving that software away.

At last year’s Add-on Con, some of the major discussions centered around add-on marketplaces and non-free browser extensions. Most parties agreed that the current system of asking for donations is not a viable revenue stream for an independent developer and that add-on developers should have a marketplace to sell their software, if they choose to do so.


Since participating in those discussions, I had been quietly considering developing a freemium add-on: an upgraded version of one of my free add-ons that comes with extra features for those willing to pay a few bucks. I was planning on waiting until a proper add-on marketplace materialized (Mozilla is working on one, as are some independent third-parties), but a few weeks ago, I decided to take the plunge on my own. (Worst case, I’d have a premium add-on ready and waiting as soon as a marketplace opened for business.) I eventually settled on freemium-izing URL Fixer.

URL Fixer is an add-on that helps you avoid typos when typing URLs in the browser’s address bar. According to the statistics gathered by Mozilla, it has been downloaded 960,000 times, and is actively used by 70,000 people. I wrote the first version in June of 2006, and it has gotten generally positive reviews, but the one request that has been consistently raised is for the capacity to add custom corrections — URL Fixer will automatically convert “google.con” to “” (because google.con is most definitely an invalid URL), but it won’t fix “” to “” (because “” might be a legitimate website).

I’ve always resisted adding any sort of correction mechanism that won’t work 100% of the time for 100% of the users (what if someone really wanted to visit, but I could justify this kind of feature in a non-free add-on, as the users who want the feature will pay for the add-on, and the users that don’t want it can continue using the free version.


To confirm my assumptions that people would pay for the ability to add their own corrections, I put a poll on the page that is shown after a user installs URL Fixer. (This page contains basic instructions on how the add-on works in order to cut down on confusion for new users.) This poll asked, “Would you pay .99 for a premium version of URL Fixer that allows you to add custom corrections?”

Out of the several thousand people that saw this page, 78 participated in the poll. Out of those 78, 29 said they’d pay for a premium version of URL Fixer. That’s 37%! You can imagine the numbers that started going through my head at this point – 37% of 70,000 current users is 26,000 users; multiply that by .99, and that’s a quick ,000. (Never mind the 1.5% poll participation rate.)


I spent a few days writing the new features, making sure that the premium version (“URL Fixer Plus“) was able to coexist with the free version if both were installed, and writing a barebones add-on marketplace. Last Friday night, I published URL Fixer Plus and the marketplace, linking them from the firstrun page of URL Fixer. I then went to sleep and waited for the money to roll in.


So how did things turn out? Of the 15,121 people that have upgraded or installed URL Fixer since I released URL Fixer Plus, 342 of them have clicked on the “Try URL Fixer Plus” link. Out of those 342, only 8 decided to actually pay the .99. For those of you not keeping track at home, that’s a conversion rate of 0.05%, a far cry from the ~37% that I expected. So, what could have gone wrong? Take your pick from these possibilities:

  • People don’t read firstun pages.
  • Anyone who didn’t participate in the poll was effectively voting “no,” putting the result much more in line with expectations.
  • Even people who did participate in the poll and said yes changed their mind when it came time to actually pay.
  • .99 is too much.
  • People want to buy the add-on, but they don’t want to use PayPal.
  • People don’t trust me enough to buy something from me.
  • People don’t expect to pay for add-ons at all.
  • All of the above.
  • None of the above.

Even though I’d consider this project a failure thus far, I’ll certainly participate in any legitimate add-on marketplaces that crop up. Several of the possible causes of URL Fixer Plus’s failure could be fixed by having a trusted, discoverable marketplace, and that’s something I can’t build on my own. In the meantime, I’ll continue to offer URL Fixer Plus as an upgrade to URL Fixer. The marginal cost of selling any more copies is essentially zero, so I have nothing to lose.


What are your thoughts? Why did I get such a low conversion rate? What could I have done better?


23 comments on “My experience with developing a freemium browser add-on

  1. Tthis is great info. Wondering if it is the wrong product?

    URL fixing is helpful but not a huge time saver or major improvement in my browsing experience.

    While power users may find the continuity in browsing crucial many don’t.

    Think framing the experiment with value spectrum of user needs and goals would be helpful.

    Before hoosuite I would have paid for your tweet bar product because it significantly improved my experience.

    Still might with the right options and integration.

    Wondering if you can play with pricing. What if you looked at current pricing as premium and worked back from there.

    Malso, maybe URL fixing is only worth .50 but you will make up for it in volume?

    At the very least you will establish a value spectrum for a class of add ons.

    Am happy to share more if you want to chat.

    Love the tools you make.

  2. Good luck with it!

    I’m sure if you’d of charged for the Web Developer extension all these years you would of made loads of cash!]

    Btw – I’d add at least a redirect or blank index page to /marketplace/

  3. Max Chung says:

    I added a redirect under /marketplace/; thanks for the tip.

    Not before I downloaded it from the index page and gave it a shot on my browser =P

    Being able to add custom corrections from the GUI is certainly a welcome addition, but I agree with Chris that enhancement is not worth $0.99. Maybe adding more value to the addon would justify the price. For example, allowing an address bar search by doing something like:

    g:google search term
    y:yahoo search term
    m:msn search term
    w:wikipedia search term

    I have seen this functionality implemented before but I do not recall where.

    Also, although there is a potential to rake in quite a bit of income, don’t depend on it as some addons break often due to browser updates, website changes, etc.

  4. whaus says:

    thanks for sharing your experiences!

    you mention the most likely error in your initial estimation yourself: people participatiting in the poll are those people the most interested in your addon – so there’s a bias towards answering “yes”.

    but besides this, there might be another variable intervening: you also added the smartlinks function, and introducing that new function + the premium version might be too much for users, and especially too much for you to get clear results for whay users buy or don’t buy the premium version.

    finally: why do you consider the project as a failure? you created and improved the addon without being paid or hoping to be paid. you now received at least 16,-$ you wouldn’t have received if you hadn’t started the project, with negligeable cost. I can see no failure here.

  5. I tried a very similar experiment with swiffout ( ) an extension to make flash games full screen (in a different way than FGM – I switched the resolution to get better performance )

    I made extensions for IE, Chrome and Firefox and released the package as an application (I hoped that people put more value in apps and I needed binaries too ). I priced at $10, then $3 then $5. I made around 9 sells, which is not too bad (but some of pure sympathy ) , but I couldn’t get any traction with a pay only version, so I stopped charging. I didn’t know what to do after talking about it on various forums and getting hackernews exposure. Ads are too costly at this level of price.

    It’s now free, and I hope to convert traffic into something at a point in the future. There is an intermediate page, that appears at a point in the use of the addon, that I could use to promote something else later.

    May be you could do something like this, use you addons to give exposure to a future non free project, the attention on the internet is scarce, so free publicity is a very good thing.

    In you case, like in my case, I think that people didn’t perceived enough value in the product to pay. Several persons told me it seemed too small. It’s not actual value, it’s perceived value.

  6. Andreas Schüttler says:

    At this point I would not pay for browser extentions. Why not? Because I change my browser to often at the moment. Last year I used Firefox. Then there was a (short) time using Opera. And at the moment I like Chrome (or Iron) the most. And every browser (-engine) has its own plugin system.
    There should be a universal plugin standard which could be used with any browser on the market.

    Just my opinion :)

  7. JFC says:

    Fascinating reading.

    My take is: $1.99 is ‘way too much to ask for such a tool. The public has been trained by Apple to expect the world for $0.99. Regardless of the internal sophistication (or whatever) of your extension or even its apparent or proven usefulness, its perceived utility minus the hassle-to-acquire/maintain-it obviously just didn’t appear great enough to justify the cost. Every price point range has an “impulse” gradient. Perhaps you should try again at $0.29 and see what happens.

  8. I think your premium add-on probably isn’t advertised like a must have add-on where people are willing to take out their credit cards and pay for it… I think if you just keep trying different techniques of marketing it you’ll eventually be successful.

  9. Wow. I literally just walked out of a meeting discussing the merits of taking freemium or going free trial followed by a monthly fee.

    I’m sorry your approach didn’t work – and will be mulling it over – will share any thoughts I have.

    Be well – and thanks for the great info.


  10. lamalice says:

    salut ;)

    moi je vais tester, et si ca me plais, bein je ferais un don!

    et oui moi je part du principe qu’il faut “aider” les petits gars qui
    n’ont pas peur de se lancer …

    continuer comme ca les jeunes, c’est( mieux que trainer les rues ) !!


  11. Lee Whalley says:

    I the UK there is a growing tide of cheapness, we have Pound shops, where everything costs one pound, these shops basically sell rubbish but at one pound people are willing to take a hit. So they will selling three cans of pepsi for one pound

    Now if we also add a free shop next door giving two cans of pepsi for free, how well do you think the pound shop is going to do?

    personally I think you should totally disassociate from the Add-on mentality when selling the paid for add-on, one can do this by not using the word; add-on, because most FF users associate Add-on with free.

    Add-on = Free

    Using the term App is probably a better option because most people know you get ad based freebies but you also get ad free paid for apps, I think its a very clever marketing scheme; you make a free app that’s mildly annoying, then make another app without the annoyance and… you get the bonus of increased functionality for being nice and paying what is a very small fee in comparison to the benefit that app would give.

    This is where being a seller comes into play, because you have to really sell that app, read up on ad selling and how they create a need by making you want it. An example would be a well known burger, they sell them to the people who have the money… the parents, they make them look healthy; yeah right, they sell them at a price a parent thinks is good value, they sell the convenience by making the outing to buy the burger a family affair thats fun; almost like a mini party. then they show you that succulent burger, with fresh crispy lettuce and tangy relish Mmmmmmm! bet ya want one don’t cha lol!

    half hour later your regretting having that burger and the coke that went with it. The best bit is they sell you something that you never get, because I’ve never had a burger from the well known burger chain that remotely looked like their ad pictures. Now that my friend, that is good marketing.

  12. Lee Whalley says:

    Oh Just read JFC post and I like his point, maybe have three or four additional features and charge an incremental price.

    URL Fixer Free: basic options for the average user. $0.00

    URL Fixer Pro: More options for the power user. $0.69

    Url Fixer Ultimate: Full version with X features its cool its hip, you know you want it. $1.29

  13. Chris,

    Another thing that you may want to consider is a hidden “value”. Just think about this thread: where several people asked you to fix the extension (including myself) but for whatever reason you have not responded to that thread.

    The reason why people asked for it is very simple – that extension is a “time saver” just because it is used more often comparably to the number of times when URL needs to be corrected in my browser’s addressbar. I use plaintextlinks many times per day and every time I do it am annoyed by holding down “ctrl” key. If I could just open new windows without using keyboard it will be great and definitely worth $1!

  14. greg says:

    survey bias –self-selection participation
    price —$1.99 is at least $1 excessive.
    problem: how to accept micro payments. android market may be a good example for micro payments.

    good luck. you should receive compensation for your work.

  15. I have been working with the Crossrider platform for several months now ( and it solves some of the issues discussed in the comments dealing with cross-browser compatibility.

    In response to your post, I am surprised that no one pointed out the flaw with your poll: it isn’t measuring what you want to measure. The real poll was when you actually charged $1.99 and counted how many people took that action. People will reply ‘yes’ to the poll just because it costs them nothing. But as soon as they have to pay $1.99, not only will they see a drop in their bank account of -$1.99 (which is insignificant), but they have to deal with finding their wallet underneath some couch cushion and clicking through the 4-step payment process. This is friction. And people hate it more than paying a buck or two. The android market and apple app markets have solved this.

    You might have more success if the payment process is frictionless. If you could somehow have a One-click buy button like Amazon, you’d probably get more conversions. Granted, I still think browser add-ons/apps are tough sells. They don’t normally add enough value by themselves to warrant me even considering a purchase. But, power users may disagree and actually pay for a premium version.

    Take care

  16. HI Chris,

    Axel here author of several thunderbird addons, my best horse in the stable being QuickFolders, which actually does pretty well in donations, around 25,000 users and frequent donation across a spectrum of 5 to 50$; I know this is an addon which is highly useful to users, so I am quote convinced some people would be interested in a registered version. I am thinking of going freemium for a long time now, but in more radical way, as a subscription model, with yearly fees. I absolutely know that the “pro” version needs to have extra features, and I have a couple of “killer” features lined up ready to go into production.

    The big problem here is the implementation: how would you propose to implement the “shop” part of this? I believe the minimum requirements would be:

    – a customer database with a key retrieval system (based on email address, as I know as thunderbird user the users will have a unique one)
    – trial + registration period: should notify user of renewal a month prior to expiry.
    – store registration key and period locally & encrypted on users machine (which poses the technical problem of understanding the host OS – I don’t even have a Mac to test)
    – accept credit cards and not just paypal

    The idea would be to offer an update to the pro version on the next release, and pointing out that certain additional features will be “pro only” and can be trialed for free for a period of time, so people can make up their minds. After expiry either remove or disable said features to create motivation to register.

    Because of the 4 points mentioned above, I have so far dragged my heels on this, but I am planning to do these possibly on the next version of QuickFolders and was wondering on where to look for help implementing them? Is there an existing commercial system that I could plug into? Marketplace has so far only been for Fx Android, so that’s a little disappointing. Also any feedback is welcome.

    ONe more thing that should be discussed is how to create a 2 tier payment system, how would you go about charging more from “power users” who really want to fund the development and those who just want to pay very small amount? I think I probably will not go for a real small amount as it is not feasible, my thought is 10$ / year to fund this project, and whoever thinks addons have to be free can use the free version. QuickFolders is unique in the sense that it has quite a high number of “Power users” who do quite complex stuff with it and save lots of hours of work. Initially I would aim for a 3 to 5 percent take up rate on the pro offer; but I have really no idea whether this is realistic

    • I’ve been thinking a lot about this. If I was going to build a “pro” add-on today, I would approach the problem in the following ways:

      1. Get Mozilla to finish the add-on marketplace that has been rumored since at least 2010. Leave the headache of managing the store to them, and you won’t have to deal with any of the worst parts of building your own store.

      2. Make a Kickstarter for the Pro version of the add-on. Get the monetary commitments before spending all of that development time.

      3. If #1 and #2 fail, build your own store, but build it in the open and allow any add-on to be hosted there. Keep the store code open source to encourage participation. Build such a good platform that Mozilla asks to hire you and have you run it for them. Until then, take a % cut of each transaction to fund the management of the store.

      I don’t envy your position, because no matter how you approach it, getting money for an add-on right now is a lot of work.

  17. As regards (1.) they have built that, but only for the mobile market. If they had built one for desktop apps (and would have included Thunderbird, which isn’t even guaranteed) I would be using it and we probably wouldn’t need a discussion on it.

    I don’t mind developing some of the functionality (like a feature restriction mechanism), I think the biggest problem is the registration part and selecting a hosting platform which guarantees continuous usage. Without having a clear idea on how to spread that risk, I wouldn’t even like to prototype. I guess asking for funds via kickstarter might be an idea, but who would be motivated to spend money in order to make a free product paid?

Leave a Reply

Your email address will not be published. Required fields are marked *