---
title: "2021.5 release notes"
canonical_url: "https://www.nutrient.io/guides/web/release-notes/2021-5/"
md_url: "https://www.nutrient.io/guides/web/release-notes/2021-5.md"
last_updated: "2026-06-09T10:25:14.552Z"
description: "Explore the new AP stream rendering in PSPDFKit 2021.5 and understand important migration steps for improved performance in older browsers."
---

# Migration guide for PSPDFKit 2021.5

With [PSPDFKit for Web 2021.5](https://www.nutrient.io/blog/pspdfkit-web-2021-5-document-crop-accessibility/), AP stream rendering is now enabled by default for all annotations. The difference in the visual appearance of the annotations shouldn’t change noticeably, except for those cases where the AP stream actually differs significantly from what the annotation properties describe.

Performance of initial AP stream rendering in Server mode has been improved as well, except for in some older browsers — namely old Safari versions and IE11.

Internet Explorer 11 is no longer supported in our Web SDK [as of version 2022.5.](/blog/pspdfkit-web-2022-5-content-editor-and-measurement-tools/) Edge 18 is no longer supported in our Web SDK [as of version 2023.2.](/blog/pspdfkit-web-2023-2-comment-mentions-notifications/)

In those cases, annotation rendering in Server mode may appear slower, especially if AP stream rendering wasn’t enabled before.

As a workaround, [disabling AP stream](https://www.nutrient.io/guides/web/annotations/appearance-streams.md) rendering for those browsers in the configuration is the recommended approach:

```js

// `isIE11` and `isOldSafari` are placeholders for browser detection flags.
NutrientViewer.load({
  isAPStreamRendered: () =>!isIE11 &&!isOldSafari
});

```

For a full list of changes, check out the [changelog](https://www.nutrient.io/guides/web/changelog.md#2021.5).

## Migrate PSPDFKit Server

If you use PSPDFKit Server, make sure you read the [2021.5 server migration guide](https://www.nutrient.io/guides/product-archives-and-deprecated-solutions.md).
---

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