OpenZPL vs Labelary

OpenZPL is a ZPL rendering API that accepts the same v1 requests as Labelary's, so most clients switch by changing the hostname. It counts the free allowance in labels rather than requests and renders PNG and PDF only, while Labelary also converts to other printer languages.

Ažurirano 2026-10-20 · Renders made with the OpenZPL engine

Who the switch is for

• You call Labelary's v1 API to render ZPL to PNG or PDF and want a second provider, or a fallback that takes the same requests.
• Your traffic is mostly single-label PNGs, where a label and a request are the same thing.
• You want the renders in the browser and from the API to come from the same engine, with a public compatibility list.

Stay on Labelary if you need output in EPL, IPL, DPL, SBPL or PCL, JSON data extraction, its image-to-ZPL or font APIs, PDF page layouts, a contracted SLA today, or an on-premise licence. OpenZPL doesn't offer those yet.

Features

Labelary facts are from its service page as read on 2026-10-20; the header behaviour was also checked with test requests (see the migration guide).

Limits and billing units

The two free tiers count different things. Labelary counts requests per day; OpenZPL counts labels, ^PQ copies and PDF pages included, so a request that returns a 50-page PDF is 1 request but 50 labels. OpenZPL's free tier is smaller on purpose: 3 labels a day without a key and 20 with a free key, to evaluate the API. Production traffic runs on a paid plan, from $29 a month and lower by country.

When a limit is hit, both answer 429 with a Retry-After header. OpenZPL's message names the limit (requests per second, labels per day or shared free capacity).

Prices

OpenZPL prices as of 2026-11-08, Labelary's as published on 2026-10-28. OpenZPL's paid plans are subscriptions by card through Stripe, monthly or yearly (two months free), priced in US dollars, and you can cancel at any time. OpenZPL counts paid plans per calendar month; Labelary counts per day.

Compare on your own traffic: if your requests return many labels each, multiply by labels per request before comparing OpenZPL's labels with Labelary's requests. Labelary's paid plans include zero data retention and a 99% or 99.9% SLA; its free plan has neither. OpenZPL never stores the ZPL of paid plans or API keys; anonymous renders may be sampled for up to 24 hours to find rendering bugs (see the privacy page).

Compatibility and differences

Accepting the same request doesn't mean drawing the same pixels. Two engines can differ in fonts, barcode details and how they read malformed ZPL. The compatibility page lists which commands the OpenZPL engine draws and which it doesn't support yet. Differences we measured on 2026-10-20:

• Output formats: Labelary also converts to EPL, IPL, DPL, SBPL and PCL and has experimental JSON and ZPL output. OpenZPL returns PNG and PDF only; other Accept values get 406.
• PDF options: Labelary's X-Page-Size, X-Page-Layout and X-Label-Border aren't supported. OpenZPL puts one label per page at the label's own size.
• Linting: Labelary's X-Linter warnings have no equivalent in the API yet.
• Rendering: fonts are substitutes on both, so text widths can differ by a few dots, and the commands on the compatibility page's "not supported yet" list don't draw.

Before switching production traffic, render a sample of your real labels on both and compare them; the viewer uses the same engine as the API.