Comparison

Daily Diary with Lock vs Theo

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Daily Diary with Lock

This app provides a private space for journaling, allowing users to write, draw, record voice notes, and add photos or videos. It includes features like soundscapes for relaxation, personalized reminders, and robust security options like Face ID or passcode locks.

Highlights
  • Rich text editor
  • Sketchpad with precision tools
  • Add photos and videos
  • Record voice notes
  • Customizable soundscapes
  • Personalized reminders
  • Face ID/passcode lock
Features
Read full description

Turtle helps you keep a journal - you can write, draw, talk, record video, or take photos. It's completely private, giving you the space to comfortably express yourself. FEATURES + Write Rich text editor jam packed with formatting capabilities. + Draw Powerful sketchpad with precision mini-map so you can get the details just right. + Add Photos Enrich your journal with photos. + Shoot Videos Bring your journal to life by directly embedding videos. + Record Voice Notes Attach voice recordings to your journal entries. SOUNDSCAPES Peaceful sounds get you into a calm headspace while journaling. That's why Turtle comes with a soundscape builder. How does it work? Choose the sounds you like (e.g. birds chirping, a fire crackling, etc.), adjust the volumes, and you're ready to relax. MANY MORE FEATURES - Personalize reminders to keep the habit. - Lock journal with Face ID or passcode. - Use a custom pin to lock your journal if other people use your phone. - Journal templates and prompts to inspire you. - Beautiful journal covers. - Daily work count writing goal widget. - Vine-like video camera. - Search your entire journal blazingly fast - and more+ --- A clear mind can help us calmly navigate through the chaos of life. But to achieve a clear mind, we need to sort out our thoughts. It can be difficult task, so that's why we built Turtle. --- BENEFITS OF JOURNALING Journaling works because it helps you organize your thoughts, realize what's important, and clear your mind of junk. This makes decision-making and progress easier. However, maintaining a journaling habit can be challenging at times. You may not feel like writing or exploring a certain topic, or you may simply forget to check-in. That's where Turtle comes in as your superpower. It goes beyond traditional writing to offer drawing, voice recordings, and the ability to add photos and videos. You can also play peaceful sounds to create a calming atmosphere and set personalized reminders to ensure journaling becomes a lifelong habit. Sometimes our thoughts make it harder to reach our true potential. Fear and worrying can keep us safe from real danger, but it can also stop us from doing amazing things. Imagine a world where Michelangelo let a fear of heights stop him from painting; or imagine if 12 year old Justin Bieber let a fear of public singing stop him from making music. This world would be a lot less lively and fun. We believe everyone can make the world a better place in their own unique way, and the first step is to make sure nothing holds you back. That's why you should journal. --- PRIVACY Turtle's private journaling experience acts as a sanctuary for the mind. As a result, we do not store your journals on a remote server. Instead, everything is kept on your device and only accessible by you. Uou can also add a passcode or biometric lock to restrict app access on your device. PREMIUM: While Turtle is available download and use for free, some features require a subscription. Please see in-app for further information. Privacy Policy: https://www.saturdaytechnologies.com/privacy Terms of Use: https://www.saturdaytechnologies.com/terms

About

Theo

This app helps you stop overthinking by guiding you through a structured analysis of your worries and decisions. It uses evidence-based reasoning to show you the actual probabilities of your concerns, replacing feelings with clarity.

Highlights
  • Structured journaling for worries
  • Evidence-based probability analysis
  • Interactive what-if sliders
  • Sensitivity analysis of evidence
  • Private thinking journal
  • Bayesian reasoning framework
Read full description

"76% chance they text you by 10 AM" - Theo "90% chance he is ghosting you" - Theo "82% chance your neighbor makes $100,000 to $115,000 per year" - Theo Stop spiraling. Start thinking clearly. Just write what's on your mind. Theo asks smart follow-up questions, gathers real evidence, and walks you through a structured analysis so you can see the actual probability of what you're worried about. Most people discover their worst-case scenario is far less likely than they feel. Think of Theo as a brilliant, patient thinking partner — available 24/7 in your pocket. HOW THEO WORKS 1. Journal your worry, decision, or question 2. Theo identifies what you're really asking 3. Answer a few clarifying questions so Theo better understands your situation 4. Theo gathers real-world evidence and weighs it for and against 5. See clear probabilities, not just feelings — then explore the reasoning behind every number WHY THEO WORKS • Evidence over emotion. Theo won't tell you to "think positive." It shows you data — real evidence for and against your worry — so clarity replaces anxiety. • Built on Bayesian reasoning. The same framework used by doctors, scientists, and intelligence analysts to make high-stakes decisions under uncertainty. Theo makes it effortless. • Explore your own thinking. Adjust the evidence yourself with interactive what-if sliders. See how your conclusions shift when your assumptions change. Build critical thinking skills over time. • Sensitivity analysis built in. Theo shows you which pieces of evidence actually matter most — so you know exactly where to focus your attention. • Your private thinking journal. Every session is saved. Revisit past analyses, track how your thinking evolves, and watch your relationship with uncertainty transform. WHO THEO IS FOR • Overthinkers who spiral on "what if" scenarios • Anyone facing a tough decision — career, relationships, health, money • Anybody with curious questions (e.g. "I wonder how much money my neighbor makes?") • People with anxiety who want a concrete, evidence-based alternative to rumination • Students and professionals who want to sharpen their critical thinking • Anyone who's ever lost sleep over something that turned out fine WHAT PEOPLE ARE SAYING "I wrote down something I'd been anxious about for weeks. Theo showed me the actual probability was 4%. I slept through the night for the first time in a month." "It's like having a therapist, a data scientist, and a best friend in one app." "I use Theo before every big decision now. It doesn't tell me what to do — it helps me see clearly so I can decide for myself." Theo Plus unlocks unlimited analyses, full reasoning breakdowns, and interactive what-if exploration so you can think clearly about everything that matters. Privacy Policy: https://thinktheo.app/privacy Terms of Service: https://thinktheo.app/terms

Screenshots

Daily Diary with Lock4 screens
Theo4 screens

Verdict

The call

The clearest difference is review sentiment: Daily Diary with Lock at 86% against Theo's 0%. Daily Diary with Lock also leads on ads (none vs shown) and rating (4.6 vs 4.2). On price, update cadence, in-app purchases and monetization model there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Daily Diary with Lock sells 7 in-app purchases, starting at $2.49 per 7 days and Theo sells 9 in-app purchases, starting at $4.99 per 7 days. Whichever you choose, the download price is not the number that matters.

ReceptionRating · Positive reviews · Number of ratings

Daily Diary with Lock holds the better App Store score, 4.6 against 4.2. Both are backed by a comparable volume of ratings — 62 and 16 respectively. Written reviews point the same way: 86% of Daily Diary with Lock's written reviews are positive against 0% of Theo's.

UpkeepUpdate frequency

Daily Diary with Lock ships an update monthly, Theo every 2 weeks. The most recent releases landed on October 22, 2026 and October 20, 2026 respectively.

Scorecard5 real differences · 5 level
Daily Diary with Lock versus Theo: the parameters behind the verdict, then further details
ParameterDaily Diary with LockTheo
PriceFreeFree
Rating4.6 (62 ratings) — better4.2 (16 ratings)
Positive reviews85.7% of reviews — better0.0% of reviews
Number of ratings62 — better16
Update frequencyMonthlyEvery 2 weeks — better
AdsNo — betterYes
In-app purchasesYesYes
MonetizationFree with in-app purchasesFree with in-app purchases
DevicesiPhone, iPod — betteriPhone
Requires iOS14.0 — better16.6
Further details — not scored
Size24 MB42 MB
Age rating4+9+
DeveloperSaturday Technologies, IncKilby Labs Inc.

Customer experience

Daily Diary with Lock

All ratings60 ratings
Positive90.0%
Neutral8.3%
Negative1.7%
Written reviews49 reviews
Positive85.7%
Neutral10.2%
Negative4.1%

Theo

All ratings1 ratings
Positive0.0%
Neutral0.0%
Negative100.0%
Written reviews1 reviews
Positive0.0%
Neutral0.0%
Negative100.0%

Bugs and requests

Daily Diary with Lock

Reported bugs

6 issues
  • Locking feature not working correctly
  • App is slow
  • Cannot make new pages
  • Cannot see typing when reaching bottom of screen
  • Formatted text not displaying properly when viewing entries (but displays when editing)
Show 1 more
  • Face lock not functional

Requested features

8 requests
  • Add lines for stylus writing
  • Add calendars
  • Allow adding photos without premium
  • Improve voice diary attachment functionality (stops when screen off)
  • Allow listening to voice recordings when screen is off
Show 3 more
  • More free features
  • Option for ads instead of premium for more features
  • More notebooks without premium cost

Theo

Not enough reviews yet to summarise bugs or requests.

In-app purchases

7 purchases

Daily Diary with Lock

Subscriptions6
  • Weekly$2.497 Days
  • Monthly - Turtle Premium$5.991 Month
  • Annual - Turtle Premium3 Days trial$24.991 Year
Show 3 more
  • Annual3 Days trial$39.991 Year
  • Annual$39.991 Year
  • Annual$49.991 Year
One-time1
  • Lifetime - Turtle Premium$49.99
9 purchases

Theo

Subscriptions9
  • Theo Plus - Weekly Subscription3 Days trial$4.997 Days
  • Theo Plus - Monthly Subscription$9.991 Month
  • Theo Plus - 3 Month Subscription$12.993 Months
Show 6 more
  • Theo Plus - Semiannual Subscription3 Days trial$39.996 Months
  • Theo Plus - Annual Subscription$39.991 Year
  • Theo Plus - Semiannual Subscription$39.996 Months
  • Theo Plus - Semiannual Subscription3 Days trial$59.996 Months
  • Theo Plus - Annual Subscription$69.991 Year
  • Theo Plus - Annual Subscription$99.991 Year

Questions

Is Daily Diary with Lock free?
Daily Diary with Lock is free to download, with in-app purchases available.
Is Theo free?
Theo is free to download, with in-app purchases available.
Which has better reviews, Daily Diary with Lock or Theo?
Daily Diary with Lock is rated higher. Daily Diary with Lock averages 4.6 out of 5 from 62 ratings, while Theo averages 4.2 from 16 ratings.
Do Daily Diary with Lock or Theo have ads?
Theo shows ads; Daily Diary with Lock does not.
Which is updated more often, Daily Diary with Lock or Theo?
Daily Diary with Lock ships an update monthly, and Theo every 2 weeks. Most recently, Daily Diary with Lock was updated on October 22, 2026 and Theo on October 20, 2026.

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