Best Apps and Tools for Online Resellers

Scanning and Price Checking Apps

Amazon Seller App (Free)

The Amazon Seller App is the most widely used sourcing tool for retail arbitrage resellers. Scan any product's barcode with your phone camera and instantly see the current Amazon selling price, sales rank, number of competing sellers, and estimated FBA profit after all fees. The profit calculator factors in referral fees, FBA fulfillment fees, and shipping to Amazon, giving you a clear picture of whether an item is worth buying before you commit.

The app requires an Amazon seller account (individual plan at $0.99 per sale or professional plan at $39.99/month). Even if you primarily sell on eBay or Mercari, having the Amazon Seller App for price checking during sourcing trips is valuable because Amazon's pricing data reflects general market values across all platforms.

eBay App (Free)

The eBay mobile app includes barcode scanning and, more importantly, quick access to sold listing data. When sourcing items without barcodes (most clothing, vintage items, books without ISBNs), the eBay app lets you search by keywords and filter by "Sold Items" in seconds. This is the primary price-checking method for thrift store resellers who deal in used, unboxed, or vintage merchandise where barcode scanning is not available.

ScoutIQ (Paid, Starting Around $14/month)

ScoutIQ is the go-to app for book resellers. It scans ISBNs faster than the Amazon Seller App and displays more relevant data for book selling: FBA and Merchant Fulfilled prices, sales rank, number of competing offers, estimated profit, and historical pricing trends. The speed advantage matters when scanning shelves of books at thrift stores or library sales where hundreds of books need quick evaluation.

ScoutIQ integrates with Amazon's product database and includes features like trigger lists (alerts that highlight books matching your profit criteria) and auto-scan (continuously scanning as you move your phone across a shelf of books). For dedicated book resellers processing 50 or more books per sourcing trip, ScoutIQ's efficiency advantage over free alternatives justifies the subscription cost.

Keepa (Free Browser Extension and Paid App)

Keepa tracks Amazon price history for every product. The free browser extension adds a price history graph to every Amazon product page, showing how the price has changed over months or years. This data is invaluable for sourcing decisions because it reveals whether the current price is typical, inflated, or depressed. A product currently selling at $45 that historically ranges from $25 to $50 is fairly priced. The same product at $45 that usually sells for $65 is a temporary dip worth sourcing.

Keepa's paid tier (roughly $19/month) adds sales rank tracking, price drop alerts, and product finder tools. The price drop alerts are useful for online arbitrage: set alerts for products you want to buy when they hit a specific price, and Keepa notifies you when they do. This passive sourcing approach runs in the background while you focus on other aspects of your business.

Cross-Listing Tools

Cross-listing tools let you create a listing once and publish it to multiple platforms simultaneously or with minimal additional effort. For resellers selling on 2 or more platforms, these tools are among the highest-ROI investments because they eliminate the repetitive work of creating separate listings for each platform.

Vendoo (Free Tier Available, Paid Plans from $4.99/month)

Vendoo supports cross-listing to eBay, Poshmark, Mercari, Facebook Marketplace, Depop, Grailed, Kidizen, Vestiaire Collective, and several other platforms. Create your listing in Vendoo's interface (or import existing listings from a platform), and Vendoo pushes it to all your connected platforms. When an item sells on one platform, Vendoo can delist it from the others to prevent overselling.

The free tier allows 5 cross-listings per month, which is enough to test the tool. Paid plans increase the listing allowance. For resellers with 50 or more active cross-listed items, the time savings easily justify the subscription. Vendoo also provides basic analytics showing sales, profit, and performance by platform.

List Perfectly (Plans from $29/month)

List Perfectly is the most feature-rich cross-listing tool, supporting over 20 selling platforms. Beyond cross-listing, it includes inventory management, sales analytics, and a photo editor. The Listing Express feature uses AI to generate listing descriptions from your photos and product details, further reducing per-item listing time.

The higher price point compared to Vendoo is justified for full-time resellers managing hundreds or thousands of active listings across multiple platforms. Part-time resellers with under 100 active listings may find Vendoo's lower-cost plans sufficient.

Crosslist (Plans from $29.99/month)

Crosslist is a browser extension that copies listings between platforms. Unlike Vendoo and List Perfectly which work through their own interface, Crosslist operates within the platforms' own listing forms. It pulls data from an existing listing on one platform and auto-fills the listing form on another platform. This approach works within each platform's native interface, which some sellers prefer because it ensures all platform-specific fields are properly filled.

Shipping Tools

Pirate Ship (Free, Pay Only for Postage)

Pirate Ship offers USPS and UPS shipping rates at commercial pricing with no subscription fee, no markup, and no minimum volume. You pay only for the postage. Rates are typically 10% to 30% lower than buying postage directly from USPS.com or at the post office counter. Simple Rates, Pirate Ship's version of flat rate shipping, offers fixed prices based on package weight regardless of destination, which simplifies cost calculation.

Pirate Ship integrates with eBay, Etsy, and Shopify for automatic order import. You can also create standalone labels for platforms without direct integration (Mercari, Poshmark when using your own shipping). The interface is clean and fast, making batch label creation efficient for resellers shipping 10 or more packages daily.

Thermal Label Printer

A thermal label printer eliminates the need for ink, toner, tape, and scissors when printing shipping labels. You print directly onto adhesive 4x6 labels that peel and stick onto packages. Popular models include the Rollo (around $200), Munbyn (around $100 to $150), and Brother QL-1110NWB (around $140). The Rollo is the most popular among resellers for its reliability and speed, while Munbyn offers good performance at a lower price.

The investment pays for itself within a few months. Ink costs for printing labels on a standard printer run $0.10 to $0.20 per label. Thermal labels cost approximately $0.03 to $0.05 per label with no ink cost. At 30 shipments per week, the savings add up to $100 to $200 per year while also saving the time of cutting and taping paper labels.

Postal Scale

An accurate postal scale is non-negotiable for any reseller who ships items. The Accuteck ShipPro (around $25) weighs packages up to 86 pounds with 0.1 oz accuracy. Accurate weight measurements prevent two costly errors: overestimating weight (paying more in postage than necessary) and underestimating weight (triggering postage due charges that frustrate buyers and lead to negative feedback).

Inventory and Business Management

Spreadsheets (Free)

Google Sheets or Excel is sufficient for tracking inventory, purchases, sales, and profit for most solo resellers. Create columns for: date purchased, item description, source, purchase price, platform listed, listing price, date sold, sale price, platform fees, shipping cost, and net profit. This data lets you calculate your actual profit by category, source, and platform, which guides smarter sourcing decisions. Templates are freely available online, or build your own to match your workflow.

Seller Tools by Platform

Each platform offers built-in analytics and tools. eBay's Seller Hub provides sales performance data, listing optimization suggestions, and competitor pricing insights. Poshmark's My Stats shows your closet performance, community shares, and offer activity. Amazon's Seller Central includes business reports, inventory health, and advertising tools. Mercari's seller dashboard shows earnings, shipping trends, and rating history. Use these built-in tools before investing in third-party analytics.

Accounting Software

Once your reselling income exceeds $5,000 per year, basic accounting software simplifies tax preparation significantly. Wave (free) handles invoicing, expense tracking, and basic financial reporting. QuickBooks Self-Employed (starting around $15/month) adds mileage tracking, receipt capture, and quarterly tax estimate calculations. At a minimum, track all expenses (sourcing costs, shipping supplies, platform fees, mileage) and all revenue by platform for accurate tax reporting. See our accounting guide for more on managing business finances.

Photography and Listing Tools

PhotoRoom (Free Tier Available)

PhotoRoom removes backgrounds from product photos and places items on clean, white backgrounds automatically. The AI-powered background removal is fast and accurate for most product types. The free version includes a watermark; paid plans ($9.99/month) remove the watermark and add batch processing. Clean, white-background photos improve listing appearance and buyer confidence, particularly on eBay where product photos are the primary selling tool.

Google Lens (Free)

Google Lens identifies products from photos, which is useful when you find an item you cannot identify at a thrift store. Take a photo of the item and Google Lens searches for visual matches, often identifying the brand, model, and current market prices. This is particularly useful for vintage items, unmarked ceramics, and electronics without visible model numbers.

Building Your Tool Stack

New resellers should start with free tools and add paid tools only when the time savings justify the cost. A minimal starter stack: eBay app (free) for price checking, Pirate Ship (free) for shipping labels, Google Sheets (free) for inventory tracking, and a $25 postal scale. Total cost: $25.

An intermediate stack adds: Vendoo ($4.99 to $24.99/month) for cross-listing, Keepa free extension for Amazon price tracking, and PhotoRoom free tier for background removal. Total added monthly cost: $5 to $25.

A full-time professional stack adds: ScoutIQ ($14/month, if selling books), List Perfectly ($29/month, for high-volume cross-listing), a thermal label printer ($100 to $200 one-time), QuickBooks Self-Employed ($15/month), and Keepa paid tier ($19/month, for advanced analytics). Total added monthly cost: $50 to $80 plus equipment.

The tools that produce the highest ROI for most resellers are, in order: a cross-listing tool (saves 5 to 10 hours per week), a thermal label printer (saves time and ink costs on every shipment), and a postal scale (prevents shipping cost errors). Invest in these three before anything else.