Custom Shopify app development
A custom Shopify app for the feature you cannot install
For Shopify and Shopify Plus merchants who have hit the limit of what an installed app does: a bundle builder with your own pricing rules, a checkout extension, an address check, a sync to an ERP or 3PL. We design and build the app on Shopify’s APIs, and it runs on your store alone.
Selected workAll case studies
Happy clients
The scope is written down with a fixed price before any code, and work starts within 3–5 business days. You get a development store to click through, an update at least every 48 hours in one shared Slack channel, and a weekly call. The engineer who scoped the app builds it, and you own the code at handover.
emma&noah, a German baby brand on Shopify Plus, sells through a mix-and-match bundle creator we built, and average order value went up 61% after it launched. We also built its checkout address-validation extension, Ryzon’s custom bundle app, and integrations with ERPs, fulfilment systems and CRMs for other Plus stores.
01What is included
What custom app development includes
- 01Bundle and configurator appsMix-and-match bundles, build-your-own sets and product configurators with your pricing rules, built with Shopify Functions so the discount applies in the checkout. emma&noah’s bundle creator and Ryzon’s bundle app are both ours.
- 02Checkout extensionsCheckout UI extensions on Shopify Plus: address validation, delivery instructions, gift options, upsells and custom fields that write to the order. emma&noah’s address-validation app is one of these, and it keeps working after Shopify updates the checkout.
- 03ERP, 3PL and CRM integrationsOrders, inventory, customers and fulfilment status moving between Shopify and the systems you already run, on a schedule or on webhooks. Built with retries and a log you can read, so a failed sync is visible the same day.
- 04Admin and storefront appsEmbedded admin apps built on the Remix app template, Polaris and App Bridge, so they look like part of the Shopify admin. Storefront features ship as theme app extensions your team can place from the theme editor.
- 05Testing on a development storeEvery build runs on a development store with your theme and your other apps installed before it touches the live store. You click through it yourself, and it goes live after you sign off in the Slack thread.
- 06Handover and ownershipWe deploy the app, document it and hand over the repository. You own the code and can have anyone maintain it. If you want us to keep it updated as Shopify’s APIs change, that is covered by ongoing support.
02Featured project
Shopify PlusConfigure-to-order app71 bundles migrated
Read the case studyPIXLIP
Modular LED exhibition systems sold as bills of materials. A custom configurator app, a Cart Transform function that turns one cart line into warehouse SKUs, and 71 bundles migrated off a third-party app.
03How a project runs
Four steps, and you can see every one of them
- 01A 30-minute callWe look through your store before the call and come with questions about what is slowing it down, so the time goes on your store and not on a pitch.
- 02A written scope with a fixed priceWhat we will build, what it costs and when it starts, on one page. Most projects start within 3–5 business days of you saying yes.
- 03Build in the openA shared Slack channel, a staging store you can click through at any point, an update at least every 48 hours and a call every week.
- 04Launch, then stay closeWe launch, watch the first weeks of data and fix what the data says to fix. Most clients keep us on for the next thing.
They said it on camera
Press play to hear themFounders and managers we worked with, in their own words.
Laura SchlaphorstProduct Owner eShop, Ryzon
Hassan FarhatFounder & CEO, Krafted
Grumspot's team successfully revamped the SEO ReRank app. The team made sure I'm kept up to date on the progress of the project at all times and were very quick to adapt any requested changes.
Mladen GrozevFounder, Meliora Web
Irakli LobjanidzeFounder & CEO, ABsolutely
Michael FenlonCMO, Nutri-Genetix
Very competent team who do the work diligently and professionally while still maintainting an agile approach to accomodating changing business needs.
Matthew WebbCTO, Top Screen Media
Andreas MüllerE-Commerce Manager, Emma & Noah
Martin HanewaldCTO, Simply Legal GmbH
We're impressed with their professionalism and quick reaction times to issues and requests.
Miroslav AntonovCo-Founder, Spoon
Danny ShislerCTO, The Floorr
Divyansh OjhaFounder & CEO, Odd Bunch
We loved working with Grumspot! They created a custom app for our Shopify checkout that fixed our address issue perfectly. Their quick and effective solution made a big difference for us. Highly recommend!
Andreas MüllerE-Commerce Manager, Emma & Noah
Grumspot were exceptionally great to work with. They always offered their best advice and were readily available. I thoroughly enjoyed working with them and highly recommend them.
Yash RanadiveFounder, RealityShop
It has been a pleasure working with Grumspot, and we are extremely satisfied with their services. Their communication was exceptional, and their meticulous attention to detail in data gathering stood out. Grumspot consistently exceeded expectations in their deliverables, completing the project on time and providing unwavering support for any questions our team had. We highly recommend Grumspot for any Shopify Plus projects and look forward to collaborating with them again in the future.
Sam CutroniCEO, DataTools
Working with Grumspot was a pleasure. They were highly professional in their communications and the final work product, even under a tight deadline.
Adam BrecklerCo-Founder and Head of Product @ Better Health
04Questions
Questions about custom Shopify apps
Tell us what your store needs.
Get in touch
Send a few lines about the store and what is slowing it down. We read it, look at the store, and come back with questions and a price range.