Building A $1K MRR Kindle Productivity Tool To Limit Screen Times

Published: August 12th, 2023
Daniel Nguyen
Founder, KTool
from Ho Chi Minh, Ho Chi Minh City, Vietnam
started February 2022
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Hello! Who are you and what business did you start?

Hi, My name is Daniel Nguyen and I’m the founder of KTool, a productivity tool for Kindle owners. KTool allows you to send news articles, newsletters, and RSS feeds to your Kindle.

Our most loved feature is the ability to bundle content from multiple sources into one daily magazine. Think Mailbrew but for Kindle.

Our ideal customers are busy professionals who spent a lot of time working in front of the monitor. After a long day at work, instead of spending even more time scrolling social media or news sites, you can read all those interesting articles on your Kindle.

KTool recently reached USD 1,000 in monthly recurring revenue (MRR).


What's your backstory and how did you come up with the idea?

I love building things on the Internet. The first dollar I earned from the Internet was roughly 15 years ago when I was selling a plugin for an open-source forum software called Invision Power Board. Since then I mostly do software consulting & building side projects for fun.

The idea of KTool first came to my mind when I was reading "Ask HN: I'm a software engineer going blind, how should I prepare?"

I've been wearing glasses since I was 5. My right eye is blind. Doctors said there is no chance to cure it.

I was genuinely scared. Like holy crap, if my left eye stops working, my life is done. Since then I've been very conscious about time spent on computer screens.

That's when I started using Kindle-related products: to offload as many reading materials as possible to the Kindle. Then I ran into multiple limitations, leading me to build KTool, a tool to send your favorite online content to Kindle: blog posts, Twitter threads, Hacker News discussions, RSS feeds, newsletters...

I didn't start it immediately. In the beginning, I tried to validate the idea by asking on Reddit. And the initial idea was a macOS app to send PDF & EPUB to Kindle. But after building it in public on Twitter, it's clear to me that people won't pay for it. So I kinda pivot into sending articles & Twitter threads to Kindle and got much better traction.

Take us through the process of building the first version of your product.

My rule when building the MVP is to solve one problem, for one use case, using one configuration.

For KTool, I wanted users to get value as quickly as possible. So I decided to not build the whole application right away. Instead, it was a super simple form where users can enter a link and then send them to their Kindle.

I purchased a landing page template for $59 and tweak it a little bit then host them on Cloudflare Pages for free. In the first couple of months, I solely focused on the core parser—which takes an article link and converts them into the native Kindle format.

Despite the UI being super basic and somewhat inconvenient, early users used it regularly and offered a lot of great feedback. I knew I’m on to something.

Later, once I’m confident with the core functionality, I decided to build a browser extension and it’s been the main product of KTool now.


Describe the process of launching the business.

I started building KTool in public in Jan 2022 and soft-launched the beta on Twitter in Feb. I keep improving the product until one day I got super lucky. Someone mentioned KTool on Hacker News. And I got a couple of sales that day, completely from strangers on the Internet.

Don’t make the mistake of spending all your time on product and development. Spend at least 50% of your time on sales and marketing.

I was selling lifetime deals (LTDs) in the early days. After a few months, I reached $3k in LTDs sales, which was pretty good. Much better than I expected.

In July I decided to stop selling LTDs and switched to selling subscriptions instead. It was quite challenging in the beginning. It didn’t gain much traction until I launched KTool on Hacker News. It was a huge success for me - KTool reached the front page and stayed #2 for almost 2 days.

The biggest learning during this period was to be vulnerable and tell my story on why I built the product. I was afraid that it would feel too personal, but to my surprise, it was well received. You can see the personal & friendly tone in my landing page copy.


Since launch, what has worked to attract and retain customers?

In the early days, my only growth strategy was to build KTool in public on Twitter. It was both for building a personal brand and to get quick feedback from early adopters.

When I started using Twitter more seriously last year, I immediately got overwhelming support from the founder & indie maker community. I’m probably not the best to talk about growing an audience on Twitter.

Entrepreneurship is exciting but it will likely be the most challenging thing in your career. Join a supportive community such as Indie Hacker or Twitter maker community.

The “strategy” that works for me is to share my lessons on bootstrapping KTool & Bolt AI. I occasionally create startup memes and people seem to love it. Some went viral and got over 1M impressions. I plug my product under the viral tweet and that’s it—pretty simple.

Twitter remains the second-best traffic source for KTool.


But spending too much time on Twitter is not scalable. At some point, I felt worn out. So I started to explore other channels. I’ve tried a few different things:

  • App Store Optimization (ASO): I developed the Safari extension for KTool and submitted them to the Apple AppStore. I learned more about ASO and was able to rank #1 for the term “Send to Kindle” on the Mac AppStore.
  • Engineering as marketing: I’ve built multiple free tools to drive traffic to KTool and to capture their email addresses
  • Email marketing: I send monthly product updates and occasional promotions.
  • Newsletters sponsorship: I reached out to a few newsletter authors on Twitter
  • I tried to run a few Google Ads campaigns
  • Recently I’ve been putting more effort into SEO and started to see promising results.

ASO is the most performing channel for KTool now. It constantly brings traffic without me doing anything. I think the reason it works is because people actively looking for a solution to spend less time on the computer.

Unlike the iOS AppStore, the Mac counterpart is not as competitive. I was able to rank #1 for a few important keywords on the Mac AppStore, but it’s like #70 or so in the mobile AppStore.

“Engineering as marketing” works pretty well but it’s like launching another product. As a solopreneur, I find it hard to maintain these free tools and keep building new ones.

Paid Ads don’t seem to work. The CAC is too high for a $5/mo product like KTool.

I got mixed results from newsletters sponsorship. Similar to running paid ads, the CAC is too high to be sustainable. So in the end, I decided to not pursue it further.

How are you doing today and what does the future look like?

KTool recently reached $1K monthly recurring revenue. Here is our MRR performance for the past 12 months:


My strategy now is simple: to double down on what works. That means investing more time in ASO & SEO.

I started working with a freelancer to help me build more free tools. Done right, I believe engineering as marketing can be a great strategy to grow KTool in the long run.

Recently, I launched 2 different AI products: Bolt AI & PDFPals. Both are generating revenue now and I use it to invest back into KTool.

Through starting the business, have you learned anything particularly helpful or advantageous?

My biggest learning is to choose the right market. I started KTool to “scratch my itch” without thinking much about distribution, marketing strategies, optimal pricing models…

KTool is a consumer SaaS, for a niche (newsletters & RSS readers) within a niche (Kindle users). Turns out bootstrapping a B2C SaaS is incredibly hard for someone without a marketing background like me.

It’s hard to monetize even though the traffic is not that bad. Consumers are usually extremely price-sensitive and sometimes are quite demanding.

If I was to start again, I would build a B2B SaaS instead. I’m not saying it’s easier, but it probably fits my personality and skill sets better.

What platform/tools do you use for your business?

What have been the most influential books, podcasts, or other resources?




Advice for other entrepreneurs who want to get started or are just starting out?

Getting started is always the hardest. The fear of failure is strong. Rejections hurt.

My advice is to get past that “first scary moment” as fast as you can. Just start and figure out the rest on the go. Launch fast, don’t wait until the product is perfect (hint: it never will be)

Most of your decisions are reversible, so better to make one now that you can learn from and adjust later than to not decide at all.

If you have a technical background like me, don’t make the mistake of spending all your time on product and development. Spend at least 50% of your time on sales and marketing.

Entrepreneurship is exciting but it will likely be the most challenging thing in your career. Join a supportive community such as Indie Hacker or Twitter maker community.

Where can we go to learn more?

If you have any questions or comments, drop a comment below!