Comparison

Bookends vs CrackX

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

Head to head
About

Bookends

Manage your research references and PDFs on your mobile device. Search online databases, import metadata, annotate PDFs, and organize your library. Offers basic functionality for free with optional one-time purchase and yearly subscription for advanced features like cloud sync and unlimited imports.

Highlights
  • Search online reference databases
  • Import metadata and PDFs
  • PDF annotation and markup
  • Barcode scanning for references
  • Cloud sync across devices
  • Share online libraries
  • Create multiple libraries
Features
Read full description

Bookends is the reference management app you've been looking for. The basic version offers: • Search online sites directly (arXiv, Google Books, Google Scholar, JSTOR, the Library of Congress, PubMed, PubMed Central, and Semantic Scholar) or use the built-in browser (EZProxy-compliant) to download reference metadata and PDFs (access privileges required). Searches can return a maximum of 20 references, and only 50 references can be stored in your personal database. • Use unique identifiers such as DOI, PMID, ISBN, or arXiv id to autofill references. • View the text of PDF annotations in a note stream, and create your own with our powerful PDF markup engine. • Barcode scanning, one per day. • And many more features designed to help you discover, organize, and use reference information. Standard, one-time purchase ($14.99): • No limit on searches or importing. Premium, yearly subscription ($14.99). Requires a Standard purchase. • Cloud sync with all your iOS devices and Bookends for Mac (separate purchase). • Share online libraries with colleagues. • Scan documents with Mellel Mobile*. • Create multiple libraries. • Unlimited barcode scanning. • Extract PDF annotations with deep links to annotations and text. • Convenient UI to add PDF notes to the library. • Automate your actions with Shortcuts. * iPad-only. Requires a Mellel Mobile Premium subscription. Subscription is for one year and has an auto-renew option. The subscription can be managed in iOS -> Settings > [your name] > Subscriptions. A subscription will renew if it isn't canceled at least 24 hours before the renewal date. If the subscription is not renewed, Premium will be disabled but Standard will continue to work. Terms of Service: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

About

CrackX

Features
Read full description

Optimization of a Mixed-Feed Steam Cracker App is an interactive engineering tool for evaluating steam cracking performance and CO₂ storage feasibility. The app allows users to configure operating scenarios, compare key performance indicators, estimate process outputs, and assess whether captured CO₂ can be safely stored in a geological reservoir. It includes performance metrics, feasibility results, visual charts, and report generation to support academic analysis and technical decision-making. Designed for chemical and petroleum engineering education, the app helps connect process optimization with carbon management in one workflow.

Screenshots

Bookends4 screens
CrackX4 screens

Verdict

The call

The clearest difference is in-app purchases: CrackX at none against Bookends's 2. CrackX also leads on iOS requirement (14.0 vs 18.6). On price, ads and device support 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. Bookends sells 2 in-app purchases, starting at $14.99 per year. CrackX asks for nothing beyond the download.

Scorecard2 real differences · 8 level
Bookends versus CrackX: the parameters behind the verdict, then further details
ParameterBookendsCrackX
PriceFreeFree
Rating4.7 (400 ratings) — better—
Positive reviews76.4% of reviews—
Number of ratings400 — better—
Update frequencyEvery 2 months—
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchases—
DevicesiPhone, iPadiPhone, iPod
Requires iOS18.614.0 — better
Further details — not scored
Size114 MB26 MB
Age rating4+4+
DeveloperSonny Software, LLCFatima Bazroun

Bugs and requests

Bookends

Reported bugs

3 issues
  • Incompatibility with iCloud Optimized Storage
  • Unreliable sync between desktop and mobile versions
  • Occasional data loss or corruption

Requested features

4 requests
  • Nested folders and tags for better organization
  • Automatic PDF metadata extraction
  • Improved search and filtering capabilities
  • Seamless integration with third-party services

CrackX

Not enough reviews yet to summarise bugs or requests.

In-app purchases

2 purchases

Bookends

Subscriptions1
  • Premium3 Months trial$14.991 Year
One-time1
  • Standard$14.99
None

CrackX

No in-app purchases

Questions

Is Bookends free?
Bookends is free to download, with in-app purchases available.
Is CrackX free?
CrackX is free to download, with no in-app purchases.
Do Bookends or CrackX have ads?
Neither Bookends nor CrackX shows ads.

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